The LA Times numbers come from the U.S. Military. It seems to me you will believe what you want.
Myself, I see that the various reports only show a small fraction of the total number of foreign fighters in Iraq and I cannot come to the same conclusion that you do.
The LA Times says it got the numbers from the US military. I don't see a source document. The West Point data comes from Special Operations Command and the report can be read in its entirety at the West Point website.