You must be registered to see the links
And there some rules about keys:
View attachment 4269033
So yeah Valve is a good guy, but you don't want to mess with them and trying to scam them or Steam users, that one they state clearly. Even big publishers like EA or Ubisoft offer similar prices and deals for their games on Steam, because they know they will be kicked out for not playing nicely.
So yeah if you offer your game "for free" to 5$ Patrons, but it's sold for like 10$ on Steam you are in a trouble. And I doubt it matters how long people paid said price and how much they was milked before