[notahacker]

A single skyscraper with 10x the floors needs more than 10x the structural mass to stay up, involves far more complexity and they're actually notoriously inefficient for elevators and stairs (you need to provide 100 stories of just enough capacity to service your top 10 floors, not 10 stories, and end up with potentially 30 to 40% of your overall floor area as a service core)

The economy of scale comes from using up less high value land; everything else costs more

[pests]

Sometimes skyscrapers have split elevators with lobbies at higher floors. To get to the very top you disembark half way up and then the capacity of these upper elevators can be less.