Someone may pay £50 for the bottle as a "birth-year" gift, especially as the wine is heading towards its 21st birthday.
1992 was a particularly poor vintage and, as Chateau De L'Hospital does not feature in any Bordeaux classification I can find, I doubt it would ever be able to achieve and maintain the prices you suggest. Wine Searcher
http://www.wine-searcher.com has a Chateau De L'Hospital Graves Rouge 2005, an infinitely better vintage, listed at around £12.
Personally, if you can't sell it then I'd open it and enjoy what will no doubt be a lovely mature rounded claret. But as with anything like this, you alone have to decide what to do.
One last point to note, you can't buy wine on ebay. Believe me, I've tried!
Hope this is of some interest.