That's the rub when over investing in anything...no way to get the money back out. But, he only needs ONE buyer willing to pay the price and who's to say someone won't step up and write the check?
No way I'd ever get out what I sunk into mine. If I ever did have to sell (no plans to, but "if") I'd price it reasonably and take the loss. No way around it: a 40+ year old 100HP C-150 just ain't worth forty grand. By the same token, unless you're a mechanic, there's no way to restore one for much less than forty grand (at least not from my experience).