While $1 trillion may be a staggeringly large sum for a single project, somehow I feel it this would need a lot more than that? I mean, the Central Park Tower which is similar in height was $3 billion despite being only about 40m at its max width. So if we were to extrapolate that to building enough of them side by side to extend 120km, that would cost around $9 trillion. Yes NYC construction costs are high, but I'm pretty sure building in the middle of the remote and inhospitable desert isn't going to be cheap either?
Considering Saudi Arabia's whole annual nominal GDP is only around $1 trillion I can't see them pulling this off unless it's an absolute necessity. Maybe if they used enough slave labour?
