If a seller specifies the shipping and handling costs up front, I don't see an issue. If bidders know this cost, it should be reflected in the bidding. An item with a higher stated shipping cost should sell for less than another identical item with a lower shipping cost. There is no deception anywhere to trick someone into paying more than they should.
On my own auctions, I often estimate the shipping cost because I am unable to fully package each item, weigh it, and look up the shipping cost on the internet before each auction. So, I'll give it my best guess and state a flat rate in the auction. Sometimes I'm high and make a buck or two. Sometimes I'm low and lose a buck or two.
I don't think that I am doing the bidders any disservice since they know my shipping quote up front. If I quote $5 to ship an item, I hope that they understand if the actual cost is $4 just as I don't expect them to send me an extra buck if it winds up being $6.
Todd Kuzma
Heron Bicycles
Tullio's Big Dog Cyclery
LaSalle, IL 815-223-1776
http://www.heronbicycles.com
http://www.tullios.com