$170 million adjusted for inflation ends up close to $1.2 billion in 2015. Add in the additional safety regulations (not just on the design of the bridges thems

$170 million adjusted for inflation ends up close to $1.2 billion in 2015. Add in the additional safety regulations (not just on the design of the bridges themselves, but also the added costs of safety rules for construction crews, truck drivers, etc.) we've come up with since the 70s, and $4 billion isn't a completely batshit insane number. Big projects are expensive. Also, don't underestimate the effect inflation can have on large public works projects. Inflation over the course of a 10 year project can be as high as 35% - even if inflation stays under Fed's targets. When stating dollar numbers, projects almost always do so in current, nominal dollars because that's what gets you the lowest number. And all of this is before taking into account the financing costs of a large public works project (municipal bonds are tax-exempt, but they aren't free).