Make sure you know what you are getting into. I know for a fact that a couple of companies I have come across use "house loads" or "pet loads" and not necessarily a full work up like you might do for yourself. It does work though, I have had two rifles setup by one of these individuals and they both shoot good enough for my liking. One is a muzzleloader, the other a 300 Weatherby. The muzzleloader unded up being a house load and works fine out to 400 as requested, the Weatherby they worked it up a little more, but their enthusiasm dwindled after a few test loads. Better them than me.
I do not find fault in this method, but it may not be exactly what you are looking for or expecting.