If your buyer is paying for shipping and customs then you really don't have any risk as long as you get paid before sending them. I can't imagine they would do that, but I would only proceed with the sale under those terms. Once your money or product cross out of the USA you have almost no recourse. My wife is dual citizen of both countries and we send and receive things all the time to her family. Im not familiar with your speaker brand , but if they are big and heavy the shipping / customs costs will be insane. They will most likely tax buyer for new speaker value, they won't care about them being a used product with a lower declared value.. Yuma is right on target with the small inexpensive items are about the only things that make sense once you figure in shipping and customs.
