I think the price to use the platform is not so expensive, 20$ for a mounth up to 70h is really nice, compare that to the price of a full gaming laptop and you will see that with that money you can be customer of playkey for years !
But as i get it, you have to pay for every game extra if you will want to play a full version. I dont know how this looks like, do you get your own version of the game with CD key and everything?
i think you have to bundle connect it up with your steam account to prove that you really own the game before you can start to play. i mean, you pay for the streaming connection, not for the game.