(A former commercial eBay seller here.) First, you can block a buyer from interacting with your store ever again. Second, you can leave a scathing review of the transaction and the buyer; if it's factually correct, eBay won't remove it, no matter how the buyer insists.

This eventually lowers the scammer's rating low enough to be a signal to other sellers. Such an account is either left to dust for a year or so, until the bad reviews go out of the rating-calculation window, or is replaced with a new account.

This works if you're a seller with some daily volume and selling experience. If you just want to sell a piece of your stuff at a random moment, you're at a higher risk, and are for a bigger downside if scammed.

But anyway, eBay's policies are stacked against the seller and heavily in favor of the buyer. I understand why it makes business sense.