According to Microsoft filings, Microsoft's Surface tablets continue to lose money.





For the March quarter, Surface tablets and accessories pulled in $494 million. But the company spent $539 million in chasing those sales.

For the December 2013 quarter, Microsoft spent $932 million to receive $893 million in revenue.

The Apple iPad, on the other hand, reported $7.6 billion in sales.

The trend is toward profitability, but it has a long way to go.