In Prisonblock, spending money can get you 1 of 2 things:
Respected Status; This is basically a Premium account. You regain health, nerve, stamina etc twice as quick, and get double the deposit limit in your bank account. It's a leg up for sure, but is it a game changer? Hardly, there are lots of strong players who are NOT respected.
Favors; These are the in-game currency. You can actually get them for free, but naturally you get them faster when you buy them. The uses are: Lottery entry (1 favor per entry), purchasing cell amenities (which boost your stats), increasing your cell size (to fit more amenities) and using them to buy respected status.
As favors can be gotten free, there's already somewhat of a balance, but even buying favors doesn't give you a huge advantage. The lottery can't be entered without favors, but that's no biggie because you have to be lucky to win anyways. Cell amenities can actually be bought for regular game cash from other members (who may have used favors to buy them) on the open market. Cell size is another one that can't change without favors, but again, you get X amount free per day anyway.
So these premium options not only enhance the game, but they also feed the economy (people selling off amenities etc), and while you do get a slight advantage, a cunning player without those advantages can still take you on.