I'm not exactly sure how much those games costs in the US, but based on how much I remember paying for them here:
Terraria: probably the best indie game ever, seriously if someone still doesn't know it, go give it a try.
Don't Starve: another superb game, excellent survival game, very funny and also pretty hard to master.
Risk of Rain: very fun for around 20 minute runs. game gets harder the longer you take to progress, very dynamic and really fun.
Momodora: Reverie Under the Moonlight: very nice little metroidvania, much more simplistic than the ones above, but it's pretty good.
FEZ: very clever game, somewhat short but feels very satisfying to play and solve all it has to offer.
Reventure: one of the funniest games I've ever played, you can die in a hundred different ways and discovering those while using them to learn how to actually progress in the game is a blast, DO NOT LOOK UP stuff, try it all yourself!
Kindergarten: another hilarious game, but much more messed up, trying to learn by dying in different ways and eventually uncover the mistery is a shared trait with Reventure.
Luck be a Landlord: extremely addicting game, you have to gamble in a sort of a slot machine so you can keep up paying your rent and not get expelled, very creative and hard to put down, you are warned.
Super Auto Pets: the game is free, it looks silly, and it is, but it's also very easy to get addicted on it.