Don't forget an important thing, the time to "code" each one. So I have no doubt that it's possible, but the time (money) to do it...So what would you need for an unique NPC? An ID? 24bits, List of friends 50*24bits+flags 10bits Some state 8 bits, A mood 8 bits, profession 24bits, some basic flags 10bits, a clothing set 24bits? Their place of living 24bits... (TBH i'm being generous, most static attributes could be encoded in ID or optimized in other ways - like you don't need a specific home for everyone, just building or e.g. "vanishing point"). Anyway.. that gets me to something like 1824bits. Ok, cars and drinks and wardrobe. Lets make it 20kb for each NPC, most of it being static. That gives me 5.6Gb. DDR4-3200 has tranfer rate of 25.6Gbps meaning you could run trough that full, unoptimized list 4.5 times per second.
Even 2 minutes by NPC (which is also generous) : 280K NPCs > 560K minutes > ~9333 hrs > ~388 days of work.
It's a lot
According to the wiki, Night City welcome about 6,964,425 in 2077.
You can't compare "actual" city with Night City, in theory (on the paper at least), each megabuilding houses approximately 128,000 poeple at maximum (and on a "tiny" ground surface).