This is a textbook example of supply and demand. Supply is low and demand is high. With high demand comes a higher price. Once supply is high, demand will decrease and so he will be unable to charge $350.
Personally I don't see the big deal. If people want to pay an impatience tax, then they are free to. Some people seem to be getting quite worked up over this (both here and onTCCA). Every time it's pointed out that Devastator will be released by other retailers soon, there is a post almost immediately after it going "But will it? HOW DO YOU KNOW???? What if it's not? OMG Big W had the whole world's supply of Devastators AND NOW THEYRE ALL GONE!! NOOOOOOOOOOO!!"
Or something to that effect.
Perspective people.