If you really just want to own a G3 iMac, and particularly if it's one of the more collectable color variations, like "Flower Power" or "Blue Dalmation", sure, go ahead. Try not to ship a slot-loader as the internal plastics turn brittle with age, and you will likely receive a parcel of shards if you do.

But as a tool, and for more common color variants, no, $70 is not a great price these days. Reliability is an issue with the slot loaders (I had quite a few power supplies, and even a couple of CRTs fail on me), plastics have gone brittle, and if you have to buy it new, PC100 SODIMMs are no longer so cheap because they are obsolete (DDR2 is probably cheapest right now)