Hey, Scrooge, thanks for bringing up Conan, that jogged my memory a bit.
Some of the Marvel Conan GN from the late 80s/early 90s have not been reprinted by Dark Horse yet, and sometimes go for higher prices.
Also, all of the Marvel/Epic Moebius GN titles have been going up in price because they haven't (as far as I know) been reprinted in English for nearly twenty+ years. (Again, I haven't checked on prices lately, and I have seen resistance on some higher prices over the years, specifically on eBay.) These are awesome reads, especially the Blueberry stuff, or if you have fond memories of Heavy Metal.
If and when the Moebius stuff is reprinted, prices will probably go down.
As graphic novels with original material become more exposed/praised in the mainstream media (I'm thinking Fun House, Blankets, Drinky Crow, etc.) these first printings may go up in price as well, and be bought/sold by comic and book collectors alike.
Then again, it'll all be digital soon...