Had a similar conversation this morning. Buddy of mine works with a few guys that are quite sure their "custom" builds are just as good as anything else out there. Never mind that they never shoot these sub $400 creations.
It all depends on what you want or need to do.
I can build a reliable gun for 500 or less. Might not be Krieger accurate but would be reliable. Will take a bit of elbow grease obviously.
That said I've never shot a 400 buck one in a match. But we do have a couple of them around 500 parted together for vehicle guns and I'd stake my life on either one any day.