Sadly all the goblin bows and scimitars can't just turn to gold themselves.
Why not? D&D has a lot of ways to focus on the details that are interesting and then abstract away non-salient stuff. If people are just going to go through the tedium of looting all of those bows and scimitars to then turn around and drag them off to a merchant with a bad UI, why make them do that? Just give them the gold and skip the tedium. Maybe one or two bodies have weapons on them, just in the rare case you really need a weapon of some sort right now, but just loot gold from the rest - they can assume that you sold that stuff.
Alternately, give the merchants some measure of self-interest and only have them buy things that they care about. Why in the world would any of the merchants we've seen so far (apart from the one in the goblin camp) actually want a stack of crappy shortbows (or cutting boards or half-burned candles,...)? Just make it so they won't even buy that junk unless it's something that that particular merchant would actually care about.
