I agree with you.

Refund after deducting eBay fees, storage costs, recompense for time spent attempting contact...

ie - Nothing.

If a buyer stuffed me around for 18 months, they wouldn't get a cent back. Which wouldn't happen - I'd have resolved the issue before 6 months had passed.

It is legal to keep the money after this time, and not immoral or unethical.

The buyer obviously doesn't care.