Take a look at Feature Buy slots.
You can bet usually up to 2k (100x bet) or sometimes even higher depending on brand and game and most games can pay out several thousand times your bet.
Just note that in my example, the bet is 20 and not 2k, you just pay 100 times your bet to enter the bonus.
The highest I could think of is Machina Megaways, that has a max bet of €36, and it has a jackpot of 1000x your bet, that you can win multiple times during your bonus.
I completely forgot about my favorite live game, Ultimate Texas Hold’em. Royal flush pays 500:1