I don't mind the cash shop having unique looking items, it's just vanity and f2p games do it all the time. You aren't going to look at some dude with that helmet and go "damn, dude had to do X and Y and legendary quest Z to get that!", you're going to do "Dude wasted a monthly sub on that stupid helmet, guess it looks cool." I would like to believe the added revenue would go back into the game, but more likely than not it will support their idiotic ventures such as porting D3 to consoles, making a card game, etc.
Price is a bit outrageous at the moment too, for a couple bucks it might be worth it if you wanted to look cool, but for $15? No thanks.