If you're looking at MS total investment in Xbox then they can't have made a dime overall so far. Modern accounting means you can shift stuff around in your finacial statements - but MS were down many billions before seeing some profitable quarters, plus the $ 1Billion that was set aside doesn't show yet to while looking at a few quarters they technically made some profit so far the investment in Xbox far outweighs financial returns.
If course MS has money to keep hammering away - but like all big companies not forever, and given the presure Apple is starting to put on them one side and with companies like Google on the other it'll be interesting to see how MS balance staying ahead against increasing competition in other areas while continuing to pile money into Xbox.
Try to be reasonable... its easier than you think...