if a once off - may have been an error on sellers part - the questions from ebay would be an automatic response.if more than once - it would be interesting to see how ebay deals with it.
in the past i have had people send me a large cheque, way more than the cost of item to cover " selling costs" then when the buyer turns up takes the change and goes, less a little something for my trouble . found out later its a popular form of money laundering. But in this its the seller playing games...not sure?