The problem with that is that 90% of the economy is "scalping"; buying something you have a price advantage on, marking it up and reselling it.
It'd be tough to legally define, much less enforce laws against this kind of behavior. The difference between supply and demand drives price. It is the way of the world.
Like I said, scalping tickets is already illegal in a lot of states. If Amazon bought up every other store's inventory of items and then artificially inflated the prices of those goods on Amazon.com, it'd take all of 2 milliseconds for governments to go after them. This is the same thing. And given the limited distribution channels (Ebay, Craigslist), I think it'd actually be pretty easy to enforce.