What is this about killing a kinky couple later in the game, that's just wrong. You should be able to bring them to your battle tower.
As for merchants I now destroy most of my loot or never even pick it up. I don't even have my battle tower yet and I've accumulated over 20,000 coin. Waste of time going to a merchant and selling it as they give you a pittance for it.
So unless one has to pay the lackey's in the battle tower a wage I can't forsee a need for much merchant use to get coin as coin is pretty much useless in this game.
Only thing I've paid for is enchanting and that is cheap, like 150 coin I believe. All my equipment was salvage or loot.
