Not sure what you mean? To the trader NPC sure, if you mean to other players for cash? Well morally no, and practicaly its stoopid as everything can be spawned in by a server command and transferred to a another server at at any time with a character.

So depending on what you mean yeah you could but if you (and I don't think you could have) meant for real money - only to really really stupid people.
If that was ot happen I suspect the Devs would quickly put a clause in their T&C outlawing it on the grounds the really stupid need to be protected against their own dumbassrey

But if you've not found him yet ten yeah later there is a Trader that exchanges items for gold which you can then buy stuff from him with it.