-Your bidder is only a newbie with 9 feedback. -Some ebayers are unable to view the questions at the bottom of listing due to mobile aps, so its possible he couldn't see that it was pick up only.   -You did not write PICK UP ONLY within the blurb, and the payments/postage TAB can be a bit difficult for newcomers to fathom  how to access it. Easy when you know its there, but necessarily a stand out feature.   Personally, if it was me, I would not offer a $300 freighting charge. The buyer then would have to pay you by Paypal and you never know, might just do a charge back months down the track, or get you for excessive postage or come here and complain, then get advice on how to deal with your outrageous postage claims! LOL  😉   Be nice and gently explain to your buyer that the item is PICK UP ONLY as per the terms of the listing, and that is all you can offer.  If you are feeling generous, offer your buyer a mutual cancellation, then you will get your fees back from ebay, and free to relist, and this time put it in big bold letters within the item description  PICK UP ONLY.  🙂

If you have proof of postage from Pack & Send the buyer cannot do a charge back/dispute - that's why you choose the most expensive and trackable option so it satisfied PayPal's requirements for proof of postage.