True, but the auction says he replaces the drive with a more reliable, two-gear system. I don't know what design he uses (probably just an existing, compatible setup), but if it really is more reliable, this may be a one-time fix. Whereas even if we fix the dreaded gear problem, there may be other drive train problems down the line.
I really don't want to sound pessimistic, though...nor do I want to sound overly faithful in a repair service that hasn't been personally vetted by someone on these forums (that I know of).
I'm just sayin', that I have three TG-CD's, and I would totally pay the ~$100 each for several years of trouble-free operation and Turbo gaming that would get me.
As a matter of interest, I emailed him asking him if he warranties his work at all, and if so, how long. He said "60 days unless a cap dies immediately afterward, but that kind of thing is hard to predict." (paraphrased)