100 percent coverage... sure. Okay. This is what we like to call "propaganda". Reality, it's just high density areas and thoroughfare. Plus I would sell them to put cameras up in places that are known for dissident patrons. For five years I did security integration (ip cameras, access control, etc). My business partner was apart of Seattle wanting to do the same back when they did the mesh network and I worked with a few smaller cities in the USA that wanted bids and designs.

The amount of man power to monitor, disk space, IT infrastructure, maintenance... yea. Whenever any city claims this or wants this, the reality sets in real fast as "Oh my shit, we can't do this". A real security camera, one that can run 24/7 in outdoor conditions, costs minimum $200 (Chinese ones) or you're replacing them every 1-2 years. I have had plenty of people who said I was wrong nad price gouging them. They later always had to buy the cameras I recommend before the 2 year mark hits. Dahua has decent cameras (still dog shit especially when it comes to view distance) starting at $200 each. But they do last a decent amount of time. 5 to 8 years. $500-$800 is the magic range (my opinion) for good quality Chinese cameras. But same goes for Bosch, Axis, etc. But the camera is your cheapest cost. The shear cost of all the support equipment, infrastructure, electricity, manpower... Especially with a city, it'd need such a high bitrate to have any type of resolution that matters with all that movement. You run into petabytes weekly at the minimum for a place like Beijing. Oh, I totally forgot about the video management system. Licenses are per camera on most of them. You have to pay like $50-$200 per camera for the software. Then all the servers to run the federated system. Don't get me wrong, every integrator wants a city (especially Beijing size) to say "Hey, we want 100% coverage in our city". That's retirement in one job. Granted a multi year job, depending on city. Still. Fun coupons. Lots of them.

Let me put some numbers down. 300 million cameras they say. Let's say weak, crappy 2mp camera, H.264, 12 frames a second, moderate scene activity (motion tracking to trigger recording). Save for 14 days (most cities first want 30, but request 14 after they have heart attacks from the price of storage). That's already ~100GB for those 14 days. Video and meta data take a lot of space. Multiply that by 300 million. That's ~30 billion GB. ~30mil TB. 30,000 PB. That's petabytes. Of pure no-profit storage. Just a cost sink. WD Purple drive 12TB drives (I like seagate, but the constant simultaneous read/write of a VMS, WD Purples are seriously the only real way to go) require a minimum of 2,500,000 drives. Even if they got a good deal at $250 for the bulk quantity (they're $370 consumer, and I use to get about 15%-20% off for bulk), that's $625mil in hard drives alone. Don't forget all the servers. So... many... servers... But also, redundancy, Raid5 or Raid6 depending on the firm doing it. So you need even more drives, by the ten-thousands. Oh, and the extra drives due to failure from that size of a deploy.

An average security camera of decent quality is around 5mp to 8mp. 14.44 TB to 26 TB of storage required under the same terms. Per camera. I say that's the bare minimum to even tell anything from up on a pole unless there's a decent zoom lens on the 2mp.

So when China says dumb shit like 300mil cameras in ONE city. Bullshit. Just plain bullshit. Because I promise you this. If true, I would be the one selling those damn cameras. Even one street in Beijing. I'd take ownership of that and retire. Gladly. Screw that, just the copper or glass rope alone. I'll take that piece of that pie.

TLDR: I did the math, China is full of shit about 300mil cameras in Beijing.