I'm an old fashioned stick in the mud so my short answer is 0, but let me explain why I am asking:
I was cruising around eBay and found an upcoming auction for a Farmall B. The way the seller writes the description, payment, and shipping info makes me wonder if I really want to mess with them anyway. Things like INVOICES MAY BE SENT OUT A DAY OR TWO AFTER THE AUCTION andIF YOU DO NOT GET YOUR ITEMS PAID FOR BY MONDAY, THEN YOUR PACKAGE WILL BE SHIPPED AT OUR CONVENIENCE Then I noticed there is an 18% buyers premium! If you win a live auction item, you're charged a buyer's premium, a fee paid to the seller. The buyer's premium is calculated based on the bid amount. I realize I'm an old fashioned stick in the mud, but that seems a bit excessive to me.
What do you consider a fair buyer's premium? | 
What do you consider a reasonable auction buyer's premium ?
