I had a friend have his average-sized driveway re-done with cement and it was like $60,000 which I thought was insane. Remove old cement, grade the dirt, pour new cement, smooth it out...and wait.
For starters - $60k is a LOT for a driveway. My brother's company charges $10 per square foot (at the top end) to remove and replace a driveway. This assumes the ground is appropriate (drainage is acceptable, no need for fill, etc.) This is based on 4" of concrete and steel reinforcing mesh and no subgrade prep. As with anything there are "price boosters" but that's a reasonable estimate. Average driveway is maybe 20x40, so that works out to be $8 grand max. This is in suburban South Dakota, so it might be more in larger metro areas.
A highway is nothing like a driveway. As others have pointed out, the thickness of concrete alone is double or triple (probably a minimum of 8 inches - more like 10 inches) and the reinforcement is considerably more (3/4 inch steel rebar mat 16-18 inches on center). You have to also consider that the subgrade needs at least a few inches of gravel, which is fairly expensive. It doesn't stop there - once the concrete is poured, there is typically a curing agent applied on top of the surface, and then the expansion joints have to be sawed and sealed. This is just for the road surface. I'll bet this cost also has to take into account curbing and sidewalks.
I've personally worked on both kinds of jobs - residential driveways and suburban streets. It's at least 10x more work "per foot" to do a road over a driveway. It's the difference between building a weekend "hacker project" and a production ready ecommerce website.
IMHO - the pristine unbroken roadways would be like that for only a few years/maybe a decade.
I can't seem to find anything definitive about US road depths ATM.
Napkin calc: assuming a driveway that's 20 feet wide and 30 feet long, the area will be 600 feet^2. The typical residential road's going to be something like 30 feet wide (enough for a parked car and two opposing lanes with comfort) and a guess at a block being like 1/20 of a mile, or 250 feet; that gives each city block of road about 7500 feet^2. So guessing conservatively, about one city block is probably at least 10 times larger than the driveway.
And that's before the actual road complexity. A city road also likely has to account for sewage, powerlines, telecom cables, drainage, etc. There's also a trade-off in road design: your friend likely never wants to build his driveway again, so he'll want something permanent like cement. But the city may want to make different trade-off; blacktop can be more easily maintained and expanded and upgraded than pavement, but also costs more in the long run (but pavement is more expensive up front).
It's not so simple in high density areas, but those are a small portion of the paved streets by area.
First, you create horrible traffic distortions - a place like LA or Boston simply can't load adjacent streets with more traffic and expect good outcomes. Second, you effectively shut down any business on that block, especially in an area that isn't walking friendly. You also cause huge problems for anyone living and parking at that street.
High density areas are a small portion of streets by area, but not by use (and therefore wear) or by cost. I suspect that a mile of highway is often cheaper to replace than a block of dense urban road.
Of course streets don't get shut down for weeks of prep work, but the paving will be done when the machine and crew are available and probably not at night.
This issue, to me, is hugely concerning. Why did one mile of the bay bridge cost as much to build as funding NASA for 6 years?
I'd be interested to know more about the breakdown, and I'd bet at least some municipalities are required to share it. A well trained road crew is likely pretty expensive, and as others noted, there's a lot more to a road than a driveway. Most driveways I've seen are largely cement planks, whereas a road is layers of differing materials to ensure frequent use doesn't destroy it too quickly.
As for bridges. Eugh. I dunno. Those things are often crazy expensive. I wouldn't be surprised though, since that bridge is rather large and suffers a lot more wear and tear than NASA. I mean, they just need to punch a few one-time use rockets into space, but that bridge has to deal with thousands of semis. Space is a nasty place, but I'm betting thousands of trucks barreling over is harder to deal with year in and out.
The same goes for asphalt, if that's what they're using. It'll be cheaper because it's not designed to last as long, but the scaling factors hold.
https://en.wikipedia.org/wiki/List_of_automotive_superlative...
Federal interstate MINIMUM construction standard is to assume 105500 pound semi trucks.
https://en.wikipedia.org/wiki/Federal_Bridge_Gross_Weight_Fo...
IF you could get the big trucks off the roads, maybe use very small pickup sized autonomous self driving trucks running on and 3 inch thick concrete like a driveway, THEN $600K would probably be achievable.
There are also correction factors that a SUV probably never exceeds 5 MPH on a driveway and usually doesn't park there and frankly most cheap driveways would be destroyed by a vehicle that heavy anyway, whereas the road has to survive 24x7 service at 75 MPH. The pounding the road takes at 75 MPH at 105500 pounds must simply be incredible.
[0] Link to link: http://www.vabike.org/vehicle-weight-and-road-damage/
At the very minimum, load and wear patterns are vastly different. Drainage probably looks quite different also.
I wouldn't be surprised if it requires a fundamentally different approach. Would you?
I don't know either. But if it turns out that paving your driveway to the same standard would cost $100,000 the scaling looks much better.
It is generally good to be wary of things that are superficially similar being used as proxies for one another...
Taking into account that public roads are not just random cement but usually a special mix for durability, sound properties and water resistance, and then you have all the cables and tubes going under that might need to be taken care of when removing the current layer and putting back the new one. All of this has to be done on public property by qualified staff.
Overall a 25x increase in cost seems pretty fair from an external point of view.
With safety measures erected for the public, traffic direction, signaling, etc.
[0]http://www.nj.com/news/index.ssf/2014/09/study_ranks_new_jer...
When you factor in the cost of those changes, 1.5 million seems reasonable for roughly a mile of road.