I hadn't checked up on prices for a few years, but at that time, it wasn't worth the trouble. (I fly to Japan often and was using prices there as a comparison, although I can't remember what they cost there anymore.)
Your assumption of no duty isn't reasonable, IMO. Unless you travel there every week and literally have nothing of interest to buy. (I'm not in the habit of not declaring items of high value.) Being in Canada, I have to pay duties on anything over $750 CAD (~480 EUR). Also, as you're probably aware, the aluminums are dent magnets. As soon as you check one in, kiss the BNIB/LNIB designation goodbye.
As for the theoretical profit, that's assuming you could find a theoretical buyer. IMO, it'd be pretty difficult to find a stranger to plop down $1K for a damaged suitcase. Standard CL or EBay discount on a dented suitcase would demand at least 40-50% off retail.
From my real world calculations, one might eke out some money, but I'm not that hard up to lug suitcases around the world for a few $.