That's pretty much what the trading card system is though, isn't it- a parallel system to the achievement one with a randomised generation event attached similar to loot boxes? Sell them, buy them, craft badges, inflate your epeen steam level etc and every time they're traded steam and the game's publisher get a cut.
Why the hell would anyone want steam achievements though. The cards, you can trade them for in game stuff ?
You buy stuff to be able to trade it for other stuff you want ?