The selling of firearms, like most everything, the current market sets the price.
Be prepared to be offered substantially less than current market retail price when selling to gun shops, pawnshops, private gun 'flippers', versus selling to private collectors and gun enthusiasts. Resellers want / need to move them quickly and make as much profit on resale as reasonably possible and won't want to have their money tied up in slow/no sellers they have to price too high because they paid too much for.
The most impressive single collection of high quality 'investment' grade modern firearms (mostly hand guns) I ever saw in one place at the same time, bought to be resold, was piled up on a long line of end-to-end folding tables at a local pawnshop, being recorded into inventory.
None ever made it to the shop floor for sale to general public.
