Since the product is available for sale on Shabbos, and a sale could be made and paid for on Shabbos, is there any problem regarding selling and doing business on Shabbos?
I realize each case could be different but would like to know the basic halacha and take it from there.
If the product is not an item specifically for Jewish people, it is probably allowed to be sold via Ebay even if it was purchased on Shabbos because we can assume that it was bought by a non Jew. But if the article is predominantly aimed at a Jewish market then it is a problem if we know that the article was purchased on Shabbos. I heard there is a program that calculates when is Shabbos all over the world and does not allow entry into that web site on the Shabbos of the buyer.
O:CH 244:1 & Mishnah Berurah 13, O:CH 276:2