Assuming this isn't another troll thread, did you actually check the sale history? People may have changed their prices or took them off the market.

Also, the Emperor's New pieces can be just bought at a merchant by literally anyone. You're banking on them being lazy, and lots of people are plenty willing to just go there and get them for 57 gil instead of buying them for over 8000. That's quite a markup, and people probably think it's not worth it. That one in particular I imagine isn't the most popular, either.