Ed, I agree almost completely with you about the economics of questionable old lenses in barrel. If the old lens isn't very inexpensive, a modern lens in shutter at market price is usually a better buy.
I'm very much a partisan of process and aerial camera lenses in barrel, but I buy them below the bottom of the market (not easy, possible with patience) or in bundles and then resell most of the bundle. I've never written it down, but I think I can prove a theorem to the effect that in a rational world a bundle of items will never bring more, and will usually bring less, than the items in the bundle would bring if sold individually. So bundles can offer a nice opportunity for arbitrage. And yes, eBay is not a rational neighborhood.
But I don't agree with you about the prices G-Clarons command. They're among the most expensive barrel lenses going because they go easily into shutter. Without bothering to look at recent sales on eBay, note that in the last year I've sold three 240/9 dagor type G-Clarons for $170 +/- on eBay. This is a bit more than MW's semi-outrageous shipping for the apparently useless monstrosity.
Cheers,
Dan