Hello timkatje -
You are correct, currently the system does not factor in the cost of shipping for items when you set your Max Bid. Your Max Bid is only for the amount you would be willing to pay for the particular item you are bidding on.
However, I have forwarded your comments regarding incorporating the ship cost into a "Max Cost" field as a feature request on to our Product Management team for their consideration in a future site update.
Thanks for taking the time to let us know your thoughts regarding the service!