I think it depends on what you bring. You could do it perfectly legit. Especially if you consider that you won't have to pay sales tax when you export the item from Europe to the US for example. So that would save you another 20% or so. I'd use things that are much cheaper there or hard to get here. Perhaps cashmere sweaters from Scotland or certain perfumes from France. A really smart thing would be to actually bring suitcases that you can sell here, like Rimowa and Travelite from Germany. If you live in a big enough city where there are enough buyers, you can deliver personally, which saves you the payment and shipping hassle. You'd have to post on craigslist, make a contract and arrange a down payment to be sure people will buy the merchandise once you brought it back.
Till