[sokoloff]

Walls and HVAC are cheap. What’s not cheap is all the additional square footage of floor plate to make offices work (additional space in the office itself, additional space for corridors, laying out architecture to allow sight lines to natural light, etc)

[bluGill]

Outside light is not required. There are a lot of offices without any windows in the US even in these days of the open office fad.

Different countries have different rules. Check you local laws before you put in an office without windows.

[cyphertruck]

That additional footage is cheap too when measured against the costs of the salary of the additional employees you need.

In fact, offices are cheaper because you don’t need to over staff by %100 and incur all that communications overhead.