I asked them about it once. I don't remember the specifics, but yeah, it was not a great price price. I think it's like a trade-in with cars -- you really only do it if you're in a hurry or willing to pay money to avoid the hassle of selling on your own.

I might be pulling this out of my butt, but I think it was something like 40% below the street value of the item. So if you have a $100 pedal that can be had for $50-75 used, they'd probably give you $30-45 for it.

Really though, I'd recommend just asking them what their policy is. It's probably not as bad as I say it is, otherwise why would they have as much used stuff as they do?