I've sometimes conjured the "I win" button as a rhetorical device, to argue that just because something makes a game easier doesn't automatically mean you should use it. I didn't expect anyone to actually add such a feature to a significant game. But Tree of Savior did.
It's called an "Instance Clear Voucher". Basically, if you're in a dungeon and someone in your party uses such a voucher, it kills all of the mobs. In the entire dungeon. Everyone in your party gets the experience, silver, and loot that they'd have gotten for clearing the entire dungeon, without having to do the work of actually clearing the dungeon. Yes, really.
Now, there are some restrictions on them. For starters, a single voucher is only good for dungeons with a level below 100. You can craft three of the basic vouchers into a two-star version that works for dungeons below level 200. But for level 200 dungeons and up, you can't use instance clear vouchers. For comparison, the level cap is currently 330.
Furthermore, they're decently rare, so it doesn't turn into all instance-clear vouchers all the time. If I hop into the queue at a random time, I'd expect someone to use such a voucher maybe 20% or 30% of the time. If that happens, the free clear is quick, so I jump back into the queue to follow it with a real dungeon clear. People who are going to use a voucher use it at the start of a run, not halfway through, so it doesn't get pulled out as an unexpected surprise far into a run.
Dungeon runs per day are also limited, so a whale can't just use 100 instance clear vouchers in a row to be instantly level 200. You typically get two runs of a given dungeon per day, or three for subscribers.
But here's the really shocking thing. Did you interpret my post thus far as being, "Tree of Savior put something stupidly overpowered in the item mall"? Because I said no such thing. The game has such an item mall, as it's a "free to play" game, though the most important thing in the item mall by far is a "token", basically a monthly subscription. But instance clear vouchers aren't in the item mall.
Now, whales who want to buy a ton of instance clear vouchers sort of can. Whales you want to stock up can buy tokens (basically, a month's subscription), sell them on the auction house for silver, and use the silver to buy instance clear vouchers from other players. But the actual source of the vouchers is as a fairly rare drop from mobs, and there are only so many to be had. To go that route, you'd expect to pay about $2 per voucher.