Cash Gate

A Cash Gate is a character or other obstacle that makes you collect a certain (very large) amount of Global Currency before you can move on with the story. The point of such assignment is to make sidequesting and exploration your main quest for a while.

The difference between Twenty Bear Asses and this trope is that you only get bear asses from a certain source (e.g. slain bears), while money can be raised through any number of activities, giving you a much greater degree of freedom and diversity in gameplay. Additionally, having that much money at one time may put you into the dilemma of whether to advance the plot or to buy that Infinity+1 Sword lying on the shelf... and then spend many more hours raising the money all over again.

Upon completing the quest, your money may or may not be Lost Forever. Compare Beef Gate and You Require More Vespene Gas. When the only practical way to obtain currency is to exchange real money, it may be an Allegedly Free Game.

Action-Adventure

 * Epic Mickey: At certain points in the game, you need to collect enough power sparks to open up projector screens to the next part of the main game.
 * The shop in Star Fox Adventures mixes this with standard plot advancement by selling items necessary to continue the adventure for large quantities of scarabs, each of which requires a larger capacity than Fox originally has. He gets the larger scarab bags while going through the plot normally.
 * The game also features Bribe Claws, bad guy dinosaurs who will let you pass only if you pay them enough scarabs. However, there are only two in the entire game, you only have to pay them once and you can completely avoid paying the second one thanks to a nearby rocket boost.
 * You must also pay a fee to open the gate in Light Foot Village that leads to Cape Claw.
 * In Psychonauts you must purchase a divining rod which allows you to find hidden caches of arrow heads, which in turn allows you to buy a mental cobweb remover, which you need to complete the level which will take you to the second half of the game.
 * In The Legend of Zelda the Wind Waker, you may not proceed to the final dungeon until you have paid exactly 3184 rupees to Tingle.
 * A early example used in A Link To the Past when you have to pay 10 rupees to the monkey to accompany you (as long as you don't get hit) and another 100 to open the first Dark World dungeon's door.
 * The Legend of Zelda: Link's Awakening required you to buy the bow for 980 rupees. Or you could steal it, if you didn't mind never being able to return to the shop and the subsequent scarcity of arrows and bombs.
 * You could return to the shop - you had to accept being killed once, though. Also, the name on your save game, which everyone in the game calls you, was changed from whatever you had originally to Thief.
 * Castlevania: Dawn of Sorrow has a variant. It is not required to progress through the game, but there are three rooms that require the last three digits of your money to be a certain value (eg. 666) in order for them to open. Portrait of Ruin uses this for a couple of the subquests too, but in this case you don't get any more map space for it, but quest rewards.

Adventure Games

 * Freshly-Picked Tingle's Rosy Rupeeland consists almost entirely of a series of cash gates, interspersed with occasional dungeons.

Edutainment Games

 * In Oregon Trail, you can either pay for the Barlow Toll Road (which has a couple dangerous hill sections in II), or you can take the hard route by rafting down the river.

Platform Games

 * In Sonic the Hedgehog 4: Episode 2's bonus stages, you need to collect a certain number of rings to continue along the path to the Chaos Emerald. Ditto for Sonic the Hedgehog 2.
 * Getting to the special stages that give you emeralds is done in a similar way in the first game, the second game, and Sonic Colors.
 * Sonic Unleashed's most infamous feature was requiring coins to enter other parts of the game in order to complete the story. This was made more tedious and difficult by how sparce and hidden these coins were.
 * The Amazon level in Duck Tales has a cash gate at one point, although this can be bypassed with a certain glitch.
 * This is the main purpose of the aptly named Moneybags in the Spyro the Dragon series.
 * At least, it is up until A Hero's Tail, where he's there to sell you items.

RPG -- Eastern

 * In Breath of Fire I, there's a part where you have to pay 50k GP to proceed. Hardly you would have the money by now, but there's a side quest to obtain a gold bar that sells for exactly 50k GP.
 * While you aren't asked for a specific amount, Chapter 3 of Dragon Quest IV qualifies, since near the end you must buy a large amount of weapons and armor, so you need to hoard a crapload of cash. Thankfully, Random Drops during the chapter are really, really good, helping a lot. Additionally, you need 35000 gp to open the store (though you can get 25000 by selling a statue), and you need 60000 gp to build the tunnel. There's a person that will buy a certain set of weapons/armors for 60000 gp.
 * In Mario & Luigi: Superstar Saga you must collect 100 coins in the local currency (which is apparently worth a lot more than the Mushroom Kingdom's) to get past a tollbooth (the guard for which attacks you anyway).
 * In Super Paper Mario, Chapter 2-3, you need to make 1,000,000 rubees by working in a generator room after breaking one of Mimi's vases..
 * In Recettear, paying off Recette's Disappeared Dad's debt is arguably one of these. Failing to make a repayment is still the Game Over condition, but the game allows you begin New Game+ nonetheless - in fact, it's very difficult (but not quite impossible) to complete the game without doing this once.
 * Clearing the Cash Gate by making the final repayment unlocks Endless Mode, where the game continues without the money pressure, allowing you to focus on dungeons and plot; and Survival Mode, where the debt constantly ramps and can can't ever be fully paid off.
 * In Final Fantasy: The 4 Heroes of Light, there's one part of the game where Jusqua has to raise 10,000 gil in order to un-Baleful Polymorph Princess Aire, who got turned into a cat, even though . To help with this, at this point you have the option to open your own shop and, fortunately, Karl Marx DOESN'T hate your guts!
 * In Final Fantasy VIII, you need 3000 gil to ride the train to Timber and another 3000 to get to Deling City.
 * Final Fantasy VII requires two trips to the Gold Saucer, so you have to pony up 3000 gil for admission each time.

RPG -- Western

 * In Baldur's Gate II: Shadows of Amn, you have to collect 20,000 gold pieces to pay for breaking Imoen out of Spellhold. It gets reduced to 15,000 when  realize that you have a competing offer. Curiously, this happens the very moment you have 15 grand on your person for the first time.
 * In Dragon Age II, you need to gather 50 sovereigns to finance Bartrand Tethras' expedition to the Deep Roads, which finishes Act I. This money is returned to you at the start of Act II.
 * Interestingly, you can fail at this. Since there is only a finite amount of money to be had in Act 1 (~80 gold) if you finish all the side quests but come up short because you bought too much stuff, an honest dwarf investor will offer to make up the difference. In Act II he tries to extort you for more money so you get to kill him.
 * There's a character in Neverwinter Nights - Hordes of the Underdark that knows and sells true names. You are only required to get Reaper's true name so that he teleports you to the main boss because the boss also knows his true name and specifically forbid him from doing so. However, you can buy lots of other true names, some of which don't do anything, but you can even buy the main boss in question's true name and tell him to kill himself.
 * Getting the best ending in Fable III basically requires you to spend several hours doing this.
 * Fallout: New Vegas requires you to have 2000 caps on your person in order to enter the Strip. Or 500 caps to purchase a forged passport. Or hax the securitron that checks you with a high enough Science skill. Or curry a favor from the local gang leader for a fake passport. Or sneak aboard the McCarran monorail. Or pass aboard the monorail with enough NCR reputation or in Boone's company.
 * In Oblivion, in order to get master level training in mercantile, you have to have 10,000 gold on your person. However, the master trainer doesn't take the gold from you, she just wants you to have it to prove yourself worthy as a student.
 * Similarly, to advance in the early thieves guild quests you must earn money though thefts (i.e. case an NPC or house, rob them and sell their stuff to the guild's fence). As with the mercentile example above, this is just to prove yourself and they don't take any money from you.
 * If you get kicked out of any of the guilds for whatever reason (usually for stealing from or attacking a fellow member) then you have to perform a sidequest that involves either Twenty Bear Asses or this trope.
 * In Skyrim several bandits tries to invoke this on you with a "user's tax". You can either pay the "tax" or beat their heads in.
 * In Mass Effect 1, you have to get the "Rich" Achievement to unlock the Master Spectre gear. Said achievement is awarded for having a whopping million credits in your purse at once. It also overlaps with a subtle Beef Gate later on: to get even better Spectre gear, you need the "Rich" Achievement and level 50 characters.

Strategy -- Real-Time

 * A mission in Warcraft 3 requires the player to harvest 10,000 lumber to proceed to the next mission.
 * Similarly a mission in the original Starcraft had Zerg, Protoss and Terrans team up to loot a Kel-Morian Combine harvesting facility for minerals. You could either harvest it normally, or spend some of it to raid enemy encampments for more.
 * The fairly obscure RTS game Robin Hood: The Legend of Sherwood had, for a good two thirds of the game, the main task of gathering 100,000 pounds to pay for king Richard's ransom. Thankfully, if you had spent too much money on bribing guards or buying hints and had finished the main game quests while well short of that sum, the game would let you play infinite minor sidequests until you could afford to advance the plot.

Strategy -- Turn-Based

 * Heroes of Might and Magic 3 has the barbarian campaign where you're required to gather 200,000 gold to advance. The justification is fundraising for a land-grabbing campaign.

Wide Open Sandbox

 * The ostensible object of Animal Crossing games is to earn enough money to pay off your house and all expansions.
 * Endless Ocean does this in its sequel. After the initial foray into the sunken temple, the cave is closed by an earthquake. You must raise 1 million Pelagos with guided trips, treasure hunting and photography to open the cave again.
 * Boiling Point: Road to Hell had a small number of story missions and a huge open world containing multiple factions with their own side missions. In general the story missions asked for large quantities of money and the player was free to earn it however they wanted to advance the plot.
 * Grand Theft Auto Vice City: You need to buy property to progress in the game, and said property is very expensive. If you spent too much bucks on gun or safehouses and failed to buy the building that allows you to participate in street races...well it's easier to start game from a beginning. And even if you bought it, it won't be pretty anyway.
 * Grand Theft Auto San Andreas has a similar situation to Vice City - you need to buy an abandoned airfield to train your piloting skills and advance the main plot.

Non-Video Game Examples

 * Dungeon!, the boardgame.
 * In Time had excessive border tolls for moving between districts, which were larger for entry into richer areas and designed to keep poor people walled in. However, they were less than welcoming to people who did make it through.
 * In Real Life, there's a building owned by Morgan Meighen & Associates, where you need $1 million dollars to proceed beyond the soft yellow interior.