That's the rough part with acquiring characters (or anything) through the equivalent of cash-funded roulette: you can set out to spend a certain amount to attain something you want, but it might not work, and if you're sufficiently unlucky it may turn into an order of magnitude more spending than you originally intended.

While you could of course commit to only spending $X and dealing with the results even if they're unsatisfactory, this can be surprisingly difficult psychologically, combining the best of the gambler's fallacy with the sunk cost fallacy (among many other behaviors very cleverly inspired by the game's developers) into one.