This is not a pricing question rule violation because he is asking what justifies the difference.
A higher bid may be because of permit pulling
A higher bid may be because employees are sitting around the shop threatening to quit because of 25 hrs/week.
A higher bid may be because of distance from the shop
A higher bid may be because you (the customer) threw up a red flag to the salesperson as someone that may be hard as hell to please or you have asked for a specific brand of which they don't normally deal with.
If you think one if the first two bidders is off the mark t hen get a third bid. I wouldn't let the BBB member thing influence your decision. In my area there are a lot of BBB members that are some of the shoddyist contractors around.
[Edited by Steve Wiggins on 03-17-2005 at 08:19 AM]