Way too much. I bought and sold my ValveKing 212 for $320.

I see the 112's going all the time for $175-200. If you're lucky, you can get $250 for one, because of the speaker.
Spin 'round carousel when your horse isn't screwed in.

My band:
Fractured Instinct
(For fans of Death/Groove/Prog Metal)

Ibanez RGA42E
Ibanez S420
LTD H-301
Ibanez RG520
Peavey Predator USA
Douglas Grendel 725
Line 6 Pod HD500X
Agreed, unfortunately the resale is pretty bad on them, and the fact that it's a hardcore buyers market for used gear right now doesn't help at all. Anything going on Craigslist these days is a good chunk cheaper than it would have been (sans inflation) 3 years ago.

I'm selling off a lot of my gear at the moment and I get a little more depressed every day at how little I get--it's a good thing almost all of it was bought used or on close out to begin with.