Apparently it would have cost quite a bit for the medical group he was a part of to find a locum tenens to fill in for him, even though it would have been for a very short time - I think something in the neighborhood of $10,000/day. Â Locum tenens work can be extremely lucrative, if they don't mind the "transient" lifestyle.
I've got a friend that does this part of the year. The rest of the year, he makes very little doing research "for the greater good" at a large institute in the US. (I was surprised really that these MD/PHD guys doing disease research don't make a heck of a lot of money). The locum tenens work, he claims, allows him to live fairly decently, the rest of the year.