Your initial quote was compiled as if the initial bidder was without competition. It is common place throughout the country where one guy "owns" a geographic region. There is no reason for that bidder to get aggressive with his pricing, he has no other bidders to compete with.

The second bidder probably understood he had to "low ball" the bid to get the business. I looked at your plan and can tell you the latter bid was a fair bid. I would tell the first guy to go pound sand.

This is why SIPs are not the only game in town. If we all bid our work competitively we would own the industry. And with the increase in business would come better margins due to the better economies of scale we would enjoy. Any one want to change the world, give me a ring...