Part of the problem is eBay spoon feeding buyers of less than stellar intelligence. Pay Now - Pay Here - Click This. They don't have to think or read. Just look for the big buttons and pictures. They don't go into their PayPal account either. They do everything from eBay and totally miss the refunds and reinvoices. WHERE'S MY ITEM?!?
Frustrating isn't it? Go check out my feedback. This person made up their own shipping cost which was $1 different than the figure they came up with. They asked how they could get me the diff. I asked if I could refund and reinvoice. Sure that would be great thanks! I think it's over and done with, everybody's happy. Um, no, apparently not! lol Numpty!! They make it sound like I asked for $1 over my reported shipping cost. sheesh
I had a buyer of a silly craft pattern do the same thing. Sent me 3 payments all with their own shipping cost. I kept refunding with a note. Thanks for your payment however you've paid the incorrect shipping costs. Shipping was noted in the auction listing and end of auction email I sent you as $x or $y. Here is an invoice with $x shipping. It took her three tries to get it right. geeze!!