Why would you wait so long to resolve this?

Can't you open a case for Item Not Paid?

You really don't need to negotiate with a buyer. If they haven't paid after 4 days, open a case and let it runs its course.

Buyers who do not pay up need to be penalised so that those of us sellers who have our blocks in place will have buyers like this weeded out.

Since Ebay doesn't know that you have not yet been paid, the selling fees will still be yours to settle unless you can fix this.