I can't see ANYONE wanting goblin clothes. In fact, I can't see anyone wanting USED clothes. Once clothes have been worn by someone, they should really be a lot less valuable to anyone else.
I could imagine the goblin-clothes price being used for shiny new clothes. But just think what those goblin clothing items probably look and smell like! Hideous! Not worth using for rags! And the humans are really willing to trade everything for a pile of that filth? Don't they have goblins back home? Shouldn't they want, you know, actual trade goods?
Seriously, that goblin junk should be like one or two $...if that.
Humans probably don't see as many goblins as you think, so goblin articles do have value as curiosities. Goblins are mountain-dwellers while humans are plains-dwellers and forest-dwellers. I'm sure there are the occasional goblin raids on isolated villages, but goblins wouldn't want to irk the humans more than that because a human versus a goblin isn't a match at all, and humans are short-lived prolific breeders like the goblins are (so goblins wouldn't win a war of attrition against them, unlike fighting against dwarves).
Just one dwarf should carry a lot of clothes pieces, not only one. Just like one lone dwarf shouldn't haul a big and heavy rock.