Regarding the prices of steel rising 50% can't this be mitigated to some extent by buying core materials (or a proportion of) on the futures market which is specifically designed to protect the buyer from price fluctuations?
1. The general public is uninformed, half-educated, and outraged easily.
2. Money in the beginning stages of a project is relatively expensive compared to the remainder of the project.
When the bid was selected, the project wouldn't be completed for another ~10 years -- Buying steel / concrete hedges and currency futures to guarantee prices would tie up tens of millions (maybe more) for ten years with interest before the bridge was operational. If the prices of steel and concrete and returned to their historical norms, the public would likely be blaming the firm for wasting all that money on worthless financial engineering. Could you imagine the protests if it came to light that the bridge consortium paid Goldman Sachs something like 10%-15% of the cost of the bridge with nothing in return?