Cerilia isn’t the most cosmopolitan of lands (as far as races are concerned), and pretty much anything that isn’t dwarf, elf, halfling, half-elf or human is a monster. You’ll notice that nothing on that list is of the large size category, so things sized for large or bigger creatures (or technically tiny or smaller as well) doesn’t sell well since almost nobody can make use of it. Any gear or equipment not of medium or small size only sells for 40% of its market value to represent sellers having to find collectors or other specialized buyers or magically resize it themselves (see part I).
This isn’t me trying to screw you out of wealth, the vast majority of loot dropping enemies will be medium sized. It just kinda breaks verisimilitude for me when things like that happen.