Our bike coop gets good money for old rigid mountain bikes, mostly set up as commuters. They use a pricing formula based on frame material, rims etc.

I was up there yesterday and they were commenting to a retail customer how sad they will be when the supply of those bikes dries up. That was part of conversation about how all of the low end department store bikes have cheap shocks on them and that most of the LBS offerings (hybrid/mnt) have cheap shocks too.