While price is a big part of the selection process it is not the only criteria. They can also look at past performance and what they propose. Sometimes the lowest bidder doesn't offer the best value. Sometimes the low bidder doesn't win and the company with the superior technical product or service will win. Often the unsuccessful bidder will protest.

In the tanker deal the Air Force wanted Boeing to change their proposal to a smaller tanker with more range. What hurt them was the scandal with Col. Druyun. I think this reflected badly on Boeing and the Air Force wanted to save face by looking at the Airbus group after being embarassed. Then they changed the specification to a larger tanker. So Boeing was proposing what the Air Force told them they wanted.

Tanker