As a former buyer/seller with them, make sure you do your own research on the historical sales of any product you are attempting to buy or sell to TMR. If you are willing to take less and want convenience, it's one option. The other option is list it yourself, be patient, and pass along savings to the buyer directly.
They seem to try their best to learn the market values on mainstream stuff, however if you are dealing with less known, custom, or boutique products they are not familiar with, and have no data on yet, keep your expectations in check.