That's the neat part, you don't!

Sometimes they're cheaper than launch price? Or you may get exclusive cosmetics? Idk

(Not saying it's worth it)

You get 100% of a successful game and hopefully helped the small studio to be in a position where they can make more good games thanks to the success of the first one.

Your profit is not weighted in money but a more diverse landscape when it comes to games.

And if you like games and see what AAA does to the scene, you should see that als something to strife for. Or am I mistaken?

You're investing in the quality of the game, not money.

It's more like an investment in infrastructure. The city isn't making a dime from repaving roads, but they certainly are useful. It's a bit of a gamble if they'll develop potholes or even get finnished sometimes, but people want roads.