It wouldn't be hard, but who would pay scalper prices for something that they then have to run dodgy software on that may or may not jeopardize their entire ste

It wouldn't be hard, but who would pay scalper prices for something that they then have to run dodgy software on that may or may not jeopardize their entire steam account? This is a different threat model than anti-cheat. Here you just want it to be annoying enough to stop scalping.