In fact they are really expensive....
Nobody really knows what they are worth as there are a lot of hidden stuff in Level 2 and Level 3 assets, false accounting eg.
http://www.bloomberg.com/apps/news?s...U&pid=20601109), a lot of lies by CEOs, a lot of unpredictable things on the way (like credit default swap blowout)
The second fact is, that all banks made huge profits from debt bubble 2002-2007 and these gains arent coming back anytime soon. Rather the banks now and will suffer for years from bursting of this debt bubble.