Not a great deal. There are "good" and "very good" copies currently listed at prices ranging from £15 to £25. Alibris has one at £49, but they are middlemen and often impose large mark-ups on normal dealers' prices. I avoid them where possible. If selling to a dealer, I doubt if you would get more than about £10, maybe less, for G or VG: a bit more for "near fine" or "fine", I expect (these categories are very subjective, of course).