That's a scam. It doesn't cost an added $5 EMS just for one flimsy very light weight little Famicom game. The value of EMS is based upon the size/weight of the package but a little famicom cart isn't going to add that much as I've combined more than 1 Famicom cart before in shipping just last year. The dude is trying to abuse ebay policy to take you for a ride.

If worst comes to it, throw the dude under the bus and let him be a crybaby and leave you a non-payor strike. Even on multiple items it would just be one, and that's not enough to hurt you if you don't do another for like 3 or 6 months. Since you already paid, just do a reverse charge on your card or ignore ebay and call paypal directly and explain the situation and see about getting it pulled back.