RuneQuest 3rd edition books for sale

Four 3rd edition RuneQuest books in fine condition for sale -- what would be the going price?

I have four of the 3rd edition RuneQuest hardcover books (RuneQuest, Advanced RuneQuest, RuneQuest Monsters, Griffin Island) that I have flipped through once but never got to use. Now I've got an offer for them, but it seems a little low, so I wanted to hear how the market is. I see very few of them around on Amazon, eBay and RPG used book stores, so I'd like to know if they're just forgotten and despised or so rare that they disappear from the market immediately. If somebody wants to bid on them, they're welcome of course.

Thanks,
-Lars