tdracer might correct me here, but I'm guessing the development costs of the B748 were considerably lower than the A380, given the former is a modified (albeit extensively) existing airframe versus a brand new one.
Airbus have said the A380 programme will move into the black by the end of 2015, so even if they don't get any more orders, they'll get away with it, just. Boeing will sell enough freighters (which are cheaper to make than passenger aircraft anyway) to cover their investment and probably make good money in the long run.
We talk about how hard these giants are to fill, which makes it surprising to me that Lufty, Korean and soon Transaero are going to be running both simultaneously.