With Best Offer the buyer makes an offer that's the highest amount they'll be happy to pay, this includes the Buyer Protection Fee, so the seller ends up with the offer amount less that fee.
When you go to accept the Best Offer is does tell the seller exactly how much they're getting, it will show the offer price and the price less the BPF.
The only workaround to add it the buyers end is to make a counter offer of slightly more.