A Park truing stand is self-centering, but I've never seen one perfectly calibrated. As a result, if you true the wheel to the very center between the calipers, your wheel will be off-center. I have a TS-2 which is quite a bit off. I compensate by building my wheels a few millimeters over to the left. You still need to check the centering of a wheel outside the truing stand. You can use a dishing tool, but there are alternate ways. You can fashion a dishing tool with two stacks of books. Or you can just flip the wheel over in the stand (or bike) repeatedly to see if the rim has the same clearance on each side.

Pre-built wheels are priced much lower than the sum of the components. I think it makes financial sense to build your own only when you're reusing part of the wheel. Of course, we could argue that a home built wheel is a better wheel than a machine built one, but that's outside the financial question.