The real issue is that regardless of the sellers wishes Ebay does not allow discounting to allow for combined postage with the postage inclusive option. If they did then that seller would probably have discounted in order to make a sale.

It is not the free post concept that is the issue it is the implementation.

If that had been me you contacted I would have discounted, but it would have to have been a make shift workaround. Sellers put themselves at risk when they do this.