I cruised in July and got Dolce & Gabbana True Blue for $20 less than in the states and that was not including the sales tax savings.

That's a great buy especially for Dolce. I just purchased that  2 weeks ago at a regular department store. It would have been nice to save $20 bucks and 8 1/4 % in sales tax.

prices on the ship are less than dept. stores but you can get them for at least 1/2 price on Ebay. I've never had a problem or gotten a knock-off

It's refreshing that someone else thinks like I do.  I was just onboard the Miracle and we went to Nassau in the Bahamas.  I know they can't sell below certain price restrictions either onboard or in the Caribbean.  I found what I liked on the ship but waited until I came home to make my purchases on ebay.  Sorry, Carnival but I would have shopped you if the prices were lower.  It's just the smart business decision.