There are a lot of pieces in play... some things you should think about:
1. How and where do you want to record? Cloud-based systems like Nest or Ring require a subscription for storage. Something like $10-$30/mo depending on specifics. That's different than if you purchase your own DVR (digital video recorder) and store the streams in your home. Prices for DVR range from a few bucks (software on your computer) to a couple hundred (a dedicated device).
2. What do you intend to capture? Are you talking about a video-recording doorbell, or cameras spread throughout your property? Are you thinking about recording outdoors, or strictly indoors? Whether a camera needs to be low-light capable and/or weatherproof will factor into cost. You may also want to consider whether PTZ (pan-tilt-zoom) controls are worthwhile... a Nest Hello can see only what is standing in front of it, a Foscam Z2 can look at anything you tell it to.
3. How do you want to get the video signal back to the recording device? Traditional surveillance cameras operate over coax, and may or may not need external power. Newer stuff (last decade or so) are called "IP cameras" and work over a computer network. Many are wireless
for data but you still need to power them. Some IP cameras use an internal battery, others require an AC power source. Some can be powered over an ethernet cable (what's called PoE - power over ethernet). This stuff is important, since it may influence where cameras go (access to an outlet, or within range of your wifi network) and will influence cost. Often the most self-contained solutions are the most expensive. For example, a Ring Video Doorbell which is wireless and has an internal battery is about $100, whereas a run of the mill Amcrest IP camera which will require either AC power OR an PoE is about $50.
Companies like Nest and Ring have made a big deal about how easy they make surveillance, but as a guy who used to design these systems I can tell you that there are a fair number of pitfalls and no easy solution. As an anecdote, a guy I used to work with asked me my thoughts about cameras for his home, and we had this conversation. He ended up buying a Nest Hello and was very happy with it - easy to set up, worked great, good picture quality, and $250+$30/mo. Easy. Except one day when a contractor's backhoe creamed his Range Rover, and all the Hello caught was a yellow John Deere rolling past it... not the actual impact because the view was obscured by the house. Had cameras been out at the edges like I recommended, there wouldn't have been an argument about whether someone had moved the Range Rover or not - a camera would have recorded it sitting in the same place for days.
I would think hard about what you really want to see, and for how long you need to store it before moving forwards. You may find your best money is paying someone $1500 to install a good system for you right off the bat, rather than messing around with a couple $250 plug & play devices and signing up for a $10/mo forever commitment. Or you may not!
If you're handy and feel confident about running coax or cat5 cable around your place, and are okay with computers and comfortable setting up a DVR, then maybe your 4-camera installation is $500 and never another dime.
There are probably a lot of blogs about this stuff, though I've never looked. My $0.02 is with security and surveillance is you get what you pay for. There is no easy button, just varying degrees of utility with commensurate cost.