I personally don't see this situation as greed (well, not entirely).
Sure, Microsoft charges a lot, but people still buy anyway, so the demand is there reguardless of the price. Consider, however, that any time that popular stores (real ones) in a heavily populated areas slash their prices by crazy amounts like 67%, mobs of people show up and just about kill each other for the bargains as small as $1 for a $3 item (meaning they could have afforded the 3 dollars easily beforehand yet still go crazy over the sale price).
I don't see why this would be any different online since no site can withstand unlimited amounts of simultaneous traffic and sites do receive more bottlenecked traffic at times like these. Raise the price again, fewer people will be rushing in to buy and the site can once again stay up and running. Microsoft is happy, the website is happy, and still people buy anyway.