Browsing the open 2nd hand marketplaces in the web, intentionally looking for miniatures, figurines, orcs, knights or the like among toys and such has resulted in some finds. The same might happen in eBay from time to time, when people don't know what they have, and make no connection to warhammer or miniature games. But such methodological browsing takes a lot of time.
15-30 years ago many independent toy shops, cartoon shops, book shops and some 2nd hand retailers of cartoons had a small booth of warhammer stuff. As they went bust, this stuff ended up in ever more obscure places. So 5-10 years ago you could find real treasures in some back alley shops which had acquired their goods from various shop closures. But those treasures seem to have been located & bought by now. Haven't seen or heard of such in a long while.
-Z