This is probably the best tooltip script around today, the amount of detailing that went into this exceptional.
I think he has every right to ask a price for it. That also shows he has the intention to maintain it. You can't create the same thing for that price, unless you work for less then $0,25 hour.
Getting something like this working cross browser takes a lot of time. Even for commercial use, this is a bargain.
I've taken a look at his other scripts, great stuff, frequent updates. I don't think open source will be catching up any time soon.