Should I hold them to the price?

It would be nice to see the auction link... That being said the BS over the auction being for gaskets was not right.

I have sold things on eBay and under estimated the shipping so bad by not thinking about the oversize that I lost everything I got for the item and some more $$$$ out of my pocket to boot. I never said a word to the buyer because it was clearly my own fault.

I think the seller should at least offer them to you at their cost if nothing else.

I would probally let them out of the deal and post a neutral feedback stating seller could not complete transaction.
Due to the gasket switch deal I would give them a low DSR on as described.