I'm not sure I'm following the issue. Or you saying more selling vs trading is a bad thing? I'm annoyed when I see "for trade only".
You can 'trade' your gun for cash and use that same cash to 'trade' for another gun.
Why would selling keep you out of obtaining anything? If you are cash low, SELL what you'd otherwise trade. You'll have many more interested parties.
"For trade only" has kept me from expressing interest on several things I might otherwise purchase.
^^^This^^^ - Selling is just trading with cash.