The ars fell out the 26" mtb market when the industry realised that new standards were going to make them money. So its a buyers market in that sense. Stuff will hold its value until next year when the model hub you had is now 1mm wider and pretty much useless....Or that's what they want you to believe!!
Boutique carbon frames will hold some sort of value, yeah. Upper end anything will hold its value, especially if its Santa Cruz. And im not saying that just because im a fan boy. I've trawled a lot of sites - eBay, Gumbush, PB etc etc and that's the feeling I get.
You're right about trials though. A pretty much brand new (old) hex for £150 (in FS section now) with seat and headset. Total bargain for buyers.