You'll likely get your money back and not need to even return the cart. Selling reproductions without clearly stating that they are such is a huge violation of eBay terms of service and in many cases copyright law.How good is ebay at refunds if I end up with a repo gba cart and it wasn't listed as such? I'm afraid I can't tell from the pictures.
I once naively bought what I thought was a good deal on Emerald and Fire Red, but they were reproductions. I contested and eBay refunded me without me needing to return the carts, and they shut down the seller too.