If we build a space elevator for 10-20 billion USD, it would bring down the cost of building the USS Enterprise (and really, all space construction) vastly. I think a space elevator is a better thing to build!
Would a space elevator cost only $10-20B? Burj Khalifa, a half-mile high building cost $1-2B already. Hard to imagine a space elevator costing only 10-20x the price of the world's tallest building.
A space elevator would presumably need to use a range of as yet non-existent and/or unproven technologies (very long carbon nanotube ropes, etc).
If you front-load the cost of a mostly-automatable construction of a space elevator (factory in orbit spitting out woven carbon nanotubes in opposite direction like a spider's spinnerets - this is almost definitely wandering into the realm of sci-fi, but maybe?), synthesizing the manufacturing components and launching them to orbit will be the most difficult part.
And if we can refine those materials from asteroids, that cuts the resource extraction cost as well - no need to ship it to orbit. (besides, what if the manufacturing technique for said carbon nanotube ropes require a weightless environment?)
There's even research into using the earth's magnetic field to generate electric potential this way.
Then of course there's the collision and weather and so on and so forth.
Yeah. I think the 10-20b is based off of stronger carbon nanotubes. But I think we have strong enough nanotubes at the moment. However, the stronger they get, the fewer we have to use, and the cheaper it will be.
You don't even need to build all the way to orbit or even space. A 20km tall tower made out of ordinary steel with a launch accelerator built into it would dramatically reduce the cost to orbit.
My understanding is that they are now strong enough, but we can't make them long enough. We have no way to "weld" them together after their creation to make longer tubes without sacrificing their integrity.
