Ring doorbell cam and floodlight cam is $400, that's about the same as a full 4 camera system. What if someone snatches your ding dong cam? You got their picture but the got your camera. Seems like it would be easy for someone to put on a mask, grab you cam, come back in a week while your waiting for a new one.
They use security screws to lower the risk, and if it is stolen, they will replace it.