In some regions, they go for a bit more because they are not as easy to find.
However, it's safe to say that, in the U.S. & U.K., you won't get a whole lot for one. You will get more than usual though, considering yours is the last version of iMac G3... and better-yet, over-clocked.
I'd say you could get anywhere from $40-80 off of it. I wouldn't pay $80 for a G3, but I'd say that is around the market value for one. If you had a lesser model, it would not be $80, unless it's a rare model. Most of these are not old enough to be collector's items, but are too old to be worth much. They also produced TONS of these things; I have about 12 of these machines.
Given that it IS over-clocked, fully-upgraded, and is a high-end model, I suppose you could get an O.K.-amount of money from it. It is sort of hard to judge the value of most of these, though, since the prices seem to be all over the place, and different configurations are plenty.
P.S. Off-topic, but your current MacRumors rank (or higher) allows you to have an avatar!