Dell Laptop Transformer Powering 8 Cameras?

I was taught long ago by a supervisor that most ANALOG cameras (except for the BIG PTZ Domes that use 24 Volts) should be either powered independently by a 12V - 2 Amps transformer (like this one) or in the case of 4 cameras together: by at least a 12V - 4 Amps transformer with a 4 tips-adapter cable (like this one), so that each camera receives at least 1 Amp of current. And also that if I am using Cat5e network cable for power, I should at least tie both, let's say "white blue and blue together" and "white orange and orange together", for sending electricity. NOT using only 1 pair, but 2 of the 4 pairs available.

Last week I went to a customer's house to inspect a job done by another company, since he was complaining that it was the second time that the SAME CAMERA had died and that another one stopped working recently as well. Upon inspecting the power connections, I saw that the other technician used a DELL branded Laptop 19.5V - 3.34 Amps transformer for powering 8 (EIGHT) cameras together in total !!! And worse, he only used 1 pair of the network cable for each camera. He cut the power cable and joined all the camera cables together with electrical tape.

The thing is, if I do the math, 3.34 Amps between 8 cameras is only 0.41 Amps per camera. The camera should NOT have powered on, but the strange thing is that the cameras were all working OK for a couple months before they started "dying". It seems like a "delayed internal electronic decay caused by insufficient electrical current" or "sustained voltage/current drop for a long period of time" to me (for lack of a better scientific explanation). Why is that (electrically speaking) ???

Also, why am I seeing more and more technicians "saving" on independent power transformers ?? For me, it is simply bad customer service that will make the customer NOT buying from him again, once he finds out that he had cut corners. Also using independent transformers will not raise the cost too much, so it doesn't make sense to me what the technician did on this case.

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