Loss (and a pretty big one per console sold) is pretty much a lock given the following.
- both the PS4 and the XB1 were given around $400 in cost of fabrication at launch (isupply I think). The XB1 slightly more expensive if memory serves due to ESRAM and size of the chipset
- the XB1 undersold compared to its production for most of 2014, particularly early in the year and MS themselves said they were doing drawdowns on retail channels and were lowering production. That means no cost saving on size of production.
- By end of 2014 it was pretty much expected that both consoles were making around $50 per unit sold. Cf Sony saying they were profitable per PS4 sold in early/ mid 2014.
- MS not only dropped $50 on the price, returning to 0 profitability per unit, they bundled 2 THIRD PARTY games, which should easily cost around $40-$50 per bundle to MS. Ubisoft isn't in the business of banking MS after all.
Add to that the often available $50 gift card, and you'll see why it's reasonable to think that MS has been losing between $50 and $100 per bundle sold depending on the promotion.
This being said, they can take the loss and their strategy is obviously to expand the userbase, but tbh it's looking a little bit desperate. Specially this sudden return to $349 after two weeks of being outsold in January.
