It appears to be not only a case of supply and demand but also your country and exact location. I certainly wouldn't pay $60 (57euros) for an iMac G3 with a screen as you show. Having said that, here in France the G3 iMac sold in hundreds of thousands and the national ads are still full of them.
I've bought several ranging from 20euros to 60 euros (22-$63US) here in pefect condition with matching colour keyboard and mouse, and after just having a quick look on the most popular site here there are still many for sale at reasonable prices equivalent to between 22-$63US.
My Flower Power and Dalmation were both purchased for less than 100euros ($106US) each and still perform very well. Just seen a FlowerPower close to my location priced at 250euros ($264US) which sounds about right.
An even better bargain would be a
Lime Green iMac G3 (very rare) with matching mouse whch is listed at only 70euros ($74US) which I'd snap up immediately if I was still collecting early G3 iMacs.
In my experience the Lime Green and 'Grape' colour iMacs are even more difficult to find than the FlowerPower or Dalmation models.
Apart from my current collection, I had a further two G3's in perfect working order I'd picked up for very little money. Gave one away to a charity organisation recently and may do the same with the other.