Sarge, I can see where you might say that. I can "Assemble" a decent gun, if I have all the parts on hand and they are good quality parts that require little fitting and do it in a day. But it is NOT going to be a $4500 job and it is NOT going to be the best thing you ever shot. It'll be better than average to be sure, but nothing to brag about.
But that is not the way a top gunsmith makes his money. He makes his money because it takes him a LOT longer to finish the job. Not because he's dragging his feet to rack up hours, but because he is meticulous and paying attention to every little detail. And if it isn't up to his standards, it's not leaving his shop until it is. That earns you a reputation and it earns you the right to charge more than Billy Bob down at the local gun store.
It's like the difference between a Corvette and a Ferrari. A Corvette is built on the principle of "best performance using stringent production tolerances". The result is a great performing sports car for $60K. A Ferrari is built on the principle of " the best performance with zero tolerance". It is perfect when it leaves the factory or it doesn't leave the factory. The result is a sports car that takes your breath away from every aspect, every single time you drive it but it's gonna cost you half a mil.