I have two custom rifles built on 700 long actions. One is a .308 Norma Mag with a Bartlein barrel, the other is a .284 Win with a Bartlein barrel. The Norma and .284 both had the receiver faces squared up, and I lapped the lugs on the Norma and had the threads cleaned up on the .284 Win. That's as much trueing as either one of them has. The Norma has never shot a group at 100 yards larger than 3/4 MOA, even during load development, and consistently shoots in the .3s and .4s at 100 yards. I've hit 12" steel plates with boring repeatability out to 1000 yards, and made my first ever hit at 1 mile with that rifle. The .284 I'm still working on load development with, but it has already proven to shoot sub 1/2 MOA groups at 100 yards.
If you have the money and want to ring out every possible ounce of accuracy from your action and rifle, then have it trued. If you just want a rifle that will shoot sub MOA and be consistent, then rebarrel a 700 action with a good quality barrel. I'm sure people will disagree, but I have literally seen nearly a dozen factory actions that have not been "trued" and they all shoot 1/2 MOA or better. Everyone one of them has a quality barrel from Krieger, Hart, Bartlein, Brux, etc. and that's what really makes a difference.
If you're building a target rifle then you wouldn't use a 700 action anyways. If you're building a accurate hunting rifle for shots out to 1000 yards, then I don't believe having your action trued is going to make a drastic difference. Use a quality barrel, a good stock, proper and consistent reloading components and equipment, and do proper load development. You will have a rifle that is plenty of accurate enough for hunting, even out to 800-1000 yards.