Fabulous Free Market Deals

Good deal, yes? or no...?

I'd say that's around what it's worth actually. The set bonus is only worth using if you can get 6+ pieces (and even then, the 6 and 7 set bonuses are pretty crappy compared to Empress), and given the rarity of the items, that will be relatively difficult to do.
Empress Capes hold their high value because of the materials needed to craft them and getting the other 5 pieces to complete the set is relatively cheap and easy. I think most people would prefer an Empress Cape because they're Tradeable until equipped, which allows one to trade it throughout multiple accounts and use mass amounts Chaos Scrolls of Goodness and Clean Slates. You can't really do that with this unless you want to spend 4k NX per trade, and that would get expensive fast.