Since we mostly agree I don't want to spiral down into nitpicking. I'm definitely not saying that the Steam market is perfect (or even necessarily that good), or that there aren't real problems with race-to-the-bottom price competition, or anything to minimize the issues we're talking about. I'm really just saying three things, which you may or may not agree with to varying degrees:
1. Price controls are hard to get right, and getting them wrong doesn't necessarily result in a better situation than what you were trying to fix in the first place
2. The problems we are talking about are real, but likely have other solutions than price controls
3. Given (1) and (2) a price floor seems, to me, unlikely to be the best choice