3% when using Credit Card otherwise 0 is reasonable to me.  Worse are the guys that only take cash or will take a check but only with a huge upfront down payment and bank letter to go with check.  The flat max dollar amount isn't bad either, especially for those high percentage auctions.  Never understood penalizing your patrons that you need to have come to your auction and buy items.

Have to watch Purplewave, it is usually 18% as just about anything sold in KS, which a lot of their stuff is, is also subject to the near 8% sales tax.

I can count on one hand how many times I have seen a buyers premium added to an ebay auction.