Credit crunch or whatever is a weird thing. Everyone is short of money, so retailers jack their new prices up.. But then a lot of people need money so are selling their used gear to either fund new purchases or just reclaim some money.. Seems to me like most well known brands (Fender Gibson PRS Marshall Mesa etc etc) are pretty steady in prices for used stuff at the moment. There is still big demand for them and people essentially know what they're getting so they know what it's worth to them etc.
The main place I see a difference is in vintage, rare, boutique stuff. Anything that you're taking a bit of a chance on has plummeted down in price on the used market. 12 months ago any eBay listing with "boutique, rare, vintage, mojo, custom" would sell easily at a good price. Now they seem like bad things, why would someone risk £2000 on some obscure luthier built guitar they've never tried or played when they can still get a bog standard Fender Strat for £800.
It's a buyers market if you're going used. Especially if you know exactly what you're looking for. It's only going to get worse.