Depending on the location of the clamshell iBook G3, its condition, and build model
the price can vary considerably; some builds are more sought after. A few are rare.
https://www.google.com/search?q=ibook+clamshell+for+sale&ie=utf-8&oe=utf-8
https://www.google.com/search?q=ibook+clamshell+amazon&ie=utf-8&oe=utf-8
One model that was presented by a third-party (new) was a conversion to tablet;
so one such as that is most rare. You could expect one to sell for between $35.
and $400. as approximate guess. ~ Take a look at online offers, to see asking.
Or only a few where auctions may be in-progress (or closed ones, showing final)
to get an idea. Every so often a few of these are for sale in Canada/ebay.
A UK site shows other content:
http://www.atdm.co.uk/clamshell-ibooks-for-sale/
Even google search will present their limited take on this:
The search itself presents options, with offered additional choices near end of page.
So re-wording the search may reveal other items. Some sites such as etsy where
collectors or shops re-sell stuff may also have items not shown in amazon or ebay.
By using a different search engine, sometimes you can get other results. Or at least
not have your searches tracked. I've found duckduckgo may show other content.
Good luck & happy trails! 🙂