An idea about paid mods

So i got an idea today, what if Valve implemented the ability to donate to mods creators (obviously those which would prove that they made it, and the good ones of course) freely with a big disclaimer or something that there is a possibility to support the creator.
People would be able to donate directly to creator's steam account and Valve could take 50% of the value. But that's not all, there could also be rewards for donating. For example: If you donate $1, you'd get a card from the game's collection, for $5 - 6 cards, for $10 an icon, something related with the game or being a proud donator, for $20 profile background and so on. I didn't think too much about the values but you get the idea.
In my opinion that'd be a great system, because if Valve wants to make money off mods, that's ok, they could get 50% of the value donated, modders would get money (to spend on steam, so that's even more for Valve), and people that donated would get cool rewards, for being generous.

EDIT: Maybe i'm being naive to think that valve would be so generous or that much people would donate if it was only optional, but hey, I think that would look really cool.