Depends on the topography. Building Ascension Harbor's offshore breakwater would be dull routine in 5m deep water, but herculean in 100m+ deep water.

There's also the issue of Ascension Island being a live volcano. With 3 eruptions in the past couple millennia. https://pubs.geoscienceworld.org/gsa/geology/article-abstrac...

(Though if you were writing a novel about an Ascension space elevator, the volcano adds a whole extra dimension of possible drama.)

100m of concrete vs tens of thousands of km of unobtainium cable in orbit. The harbour is far easier.

Compared to the cost of building a DC, using 24K gold for all the wiring in it would be small change.

It's fine in imagination or fiction. But in the real world, the guys who sign the checks seldom buy that type of "cheap compared to" argument.

It seems like the money would be there though, right?

A functioning space elevator would immediately make you the richest person in history, I would think.

I'm sceptic about that.

I am, see above, a space nerd, formed by SciFi. But I wonder what the economical case for space colonisation above LEO, human or robotic could be. Asteroid mining is the typical use case, but again, I'm a sceptic. You'll need to mine the materials, separate them, transport to earth, down a non-realistic space elevator made from unobtainium and do all that cheaper than mining or recycling on earth. I don‘t see that for a long, long time.

European colonisation very soon had economic use cases, It started with spices, that very soon beaver furs, wood, plantations with the original sin of slavery and over the centuries the colonies developed into bigger societies which could produce industrial goods. What could Moon or Mars sell us that we want, that could rationalise a gigantic capital investment, which only could be paid back over multiple centuries? I don't see it, and I say that as a space romantic.