As a Construction Project Manager/Estimator if I were to put a conceptional estimate number to a 42,500SF Gymnasium for this area of the country the costs would probably be somewhere around $121.39 per SF = $5,159,075.
In the current bidding market we have seen most public projects coming in at an average of 20% less than the anticipated cost estimates, so if that holds true the cost could be reduced to around $4,127,260. Most of the time they can get creative with cost estimates by not including certain things or by creating lots of alternate bid items to achieve their end means. Not being able to see the full breakdown it is possible that the 2.9 million is for just the gym area alone and does not include other supporting areas. Estimates are always just educated guesses and the more information available the better you end number will be.
Just My Two Cents.
Two cents... which by Madison math would actually be four cents?