Don't care about sales? Microsoft and Sony have two different philosophies in the market. Sony wants to make money from their machine. They're in this to gain some sort of profit in a company that's been bleeding money for years. Sony already had woes last gen selling the PS3 way under cost, they don't want a repeat of that. Sony doesn't react to Microsoft like MS reacts to them all the time. It wouldn't be a profitable venture anymore.
MS on the other hand, no longer sees profit with gaming. They're gone full warchest for little gain and the one thing that's got the system moving a little better now... is adding a non-gaming element to their console. MS is in the console game to hopefully outspend their competition and tire them out. If they can't get ahead, then the idea is to spoil the market until no one else can gain from it either. From there, they can pick up the ashes. MS wants the remainder of a shrinking console market pretty badly for some reason.
MS is in a better position to give away the house. Why do they do it? To save face? Pride? Whatever the reason , their customers are seeing the benefits of it. Whether it's good for the rest of the industry or not. Only time will tell. But Sony and Nintendo don't seem as eager to unplug the drain financially to battle them.
