Salary abuse is no joke. I have watched many co-workers get "promoted" to a salary position that pays more, only to end up making less money. Granted at that company the owner had a loose relationship with the employment laws and bent moral compass.
If you already have a firm basis in the industry from either being a machinist, or engineering, or lots of other things then maybe it's time to move on. But if you still have more to learn and a secure and stable environment that meets your monetary needs to do that learning in, then maybe it's time to branch out in your current role a bit.
Also remember that while the grass might look greener on the other side of the fence, it doesn't mean they don't have a guy who goes out and paints it green every night.
