This ray has almost certainly come out of Colombia..not Brazil!
The shop owner will have most likely bought from an wholesaler hence the mistake on the country of origin. If you study offer lists like I do from Colombia they have rays called Marble Motoro and" royal" Marble Motoro, the later being silly expensive, they are generally between £250-£300 pounds to the trade so a mark up of what you have seen is very reasonable.
The trouble is the fish in question is more than likely a "ROYAL" but from the pic it is a very poor specimen (low grade), its fully developed sexually and I don't see the pattern improving, this is the risk you take when ordering wild Marbles, better buying captive bred from a reliable breeder in the States, very good quality parents rarely produce rubbish in my experience.
It will more than likely be the cheaper option also, far less chance of importing parasites......its a win win win situation.
Good luck with your choice when ever that may be.