>If the public spends less on material they can afford to build additional bridges

Except what happens is that now that we can build them cheaply they waste the same amount of money by turning what could have been simple I beams into a mirror finish exercise in "art" nobody asks for and was bike-shed into oblivion until the whole budget and more was used up. So the public doesn't actually reap any benefit. It just makes work for more parties on the dole. We don't actually get more bridges. We get a bigger racket.

Bridges are not public goods. Public goods are non-excludable and non-rivalrous. Bridges are both excludable (people can be prevented from crossing unless they pay a toll) and rivalrous (only so many people can use a bridge at once). This makes them a private good. Yes bridges are funded by governments with revenues collected from taxes, but that doesn't change their economic classification.

And the main cost of bridges is not materials, it's design, permitting, and construction. For example: Adjusted for inflation, the new San Francisco Bay Bridge span cost $8.6 billion. Its 450,000 cubic yards of concrete weigh around 1.3 million tons, for a cost of around $6,000 per ton. Concrete is $50-75 per ton, so that's 1% of the cost.

You're right. If the minimum amount is actually the minimum and not less than necessary, you don't need to exceed that.

What the poster before wanted to imply was that we sacrifice safety or sustainability or some value other than material/money (which may well be true).

And

> businesses have learned exactly how badly they can treat you and step up to that line at every opportunity.

Will help numbers in your 401k or pension plan go up.