system
Given the following post, respond as if you're commenting on Reddit:
human
[JudgeDread] How much would it cost to build an apartment building like in Mega City one? How old is the city?
gpt
The exact age of the city is a bit fuzzy, since arguably it's a successor to a number of American cities that turned into a coast-wide urban sprawl (and some that were literally paved over, like New York City), and a lot of the buildings and infrastructure predate the proper founding of the city, but the actual, legal foundation of Mega City One as an entity was in the 2030s, and as of current comics has made it up to the 2130s, and is implied via time travel that it stays a functional entity at least into the 2150s. 

As far as how much a Block costs to build, if they were working on a conventional human labor economy the cost would be monstrous. Each Block would essentially be a large town or a small city on it's own by modern standards, with more or less all the habitation space, amenities and logistics that would require. The only thing that keeps the cost from being impossible is heavy mechanization and automation (or, during really bleak times in MC1's history, press-ganged emergency human labor); most of the actual work is done by robots capable of maintaining a 24 hour work schedule without pay and with minimal safety protections. Actual cost is still likely equivalent to multiple billions in modern U.S. dollars, even with the savings provided by robot labor.