I know several people who make a living programming.
But you have to understand that these people have the ability to code in many languages so not just MQL4/5.
And so they also work on other projects as well.
You didn't ask anything about automated trading.
I also know several people who earn a living by doing that, and they are not all programmers.
I think automated trading with ea is possible and someone out there probably has done it. But "automated" doesn't mean you put your ea and leave it a month, and in the end of month you just have a good profit. There must be a continuous tweaking.
"well paid" is about the demand. And programming skill could be acquired by anyone. But to have a profitable ea and strategy, it's a loooong story and time consuming.
You might be interested to copy trading in "Signals" section.