I've put together a webapp where users can list their articles for sale with a price and the payment is done via paypal. Now caluclating the price for the payment won't really work if there is shipping cost involved and I don't have a good method for adding the shipping. I've implemented usecases for adding and listing an article and also buying the article and paying via Paypal which works, but I don't know how to do with the shipment since the seller does not know who the buyer is when listing the item. Do you have any suggestions how I can improve the solution?
See how Ebay solves this task:
It is byuer who selects shipping options. In most cases only country is required. This dialog could be accessible with
Calculate link inside shipping cost area. At the same time don't leave the shipping cost area blank, set the shipping cost for the primary or most probable country.