As the seller you are responsible for getting the item to the buyer safely.
If there is a problem then they open a Not as described dispute
You send a label for the return of what they did receive.
Once you have it back then you refund the buyer in full.
If you dont then ebay will force you to and take the money from you
You would also get a black mark on your account
You take it up with evri but it is very difficult.
That postage is very cheap for that expensive item
Was it sent insured.
If the buyer fails on ebay then they can always go to paypal if they paid that way or their card holder
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We are just ordinary members trying to help.