The question worth asking
The wrong question is “how much does a camera cost.” The real one is “who watches that camera at 3am, and what happens when a sensor reports movement while everyone's asleep.” A system without an answer to that second question is an archive waiting for someone to check later what happened — not surveillance.
What a monitoring centre actually does
The chain has four steps. Detection: a sensor or camera reports an event. Verification: an operator at the centre looks at the picture and establishes whether the cause is real. Call list: if the event is confirmed, the operator calls in the order the owner set in advance — one contact first, then the next, emergency services or the police if needed. Report: the event gets logged, so a monthly view shows what happened and when.
Comparison: monitoring against a single night shift
Staff physically guarding one site cover exactly that site, during those hours, and see nothing while on a break or away. A monitoring centre watches several locations at once, around the clock, without a break that leaves a site with no one on the other end of the line — but it doesn't replace physical presence where a hands-on response on site is what's actually needed; it calls whoever carries out that response.
When monitoring doesn't make sense
If someone is on site at all times, cameras and access control without a monitoring contract often deliver more practical value directly to that staff. If there's no agreed protocol and no contact who'd actually be called at 3am, a monitoring contract on its own has no one to notify in a way that changes anything.
Recommendation
An existing alarm or camera system can, in most cases, be connected to a monitoring centre without replacing the equipment — reviewing the installation during the site visit shows what's worth keeping. The value of monitoring is measured against the cost of having someone physically available at night and on weekends, not against the price of the camera itself.