From experience with cars isn’t the point of trade in that you get a hassle free exchange but on the flip side less than if you sold privately?
Yes, when I buy bikes I do it at a price I know I can make a profit on (or at least not make a loss) – some people are fine with that, to get rid of the bike and get some money right away.
For trade-ins though, I bung them on eBay – that way we get the fair market value.
I don’t get many MTB trade-ins, but in my experience getting 1/3 of RRP is typical. The depreciation on MTB stuff is ridiculous.