Some, but not all, machine built wheels may be correctly tensioned and stress relieved. Those that aren't, often break spokes early and often. I don't know what the price point is where manufacturers start using the top of the line machines, but it must be above the price where I've bought wheels.

Probably the best deal in wheels today is to buy machine wheels (often for less than you can buy the parts), and have a knowledgeable mechanic (perhaps you) check/increase the tension, check the true, and stress relieve the spokes.