The 600,000BTC figure is based on the maximum possible $80m slice of sales he took, no? I would think his private stash would be a good deal lower than 600,000. Still lots for the FBI to sell if they ever get the key and recover it.
Yes, now that you say that, it is. It said in the FBI report that he paid his administrators between $1,000-$2,000 a week, and who knows how many of them there were, plus the costs of running a high security operation like that would likely be pretty high. Even if he had 1/4 of that for his personal gains from the site, that's pretty damn good for 2 1/2 years of work!!