I read a post by Kirby that said that when a customer shot one of his personal rifles the customer's offer couldn't be ignored and the rifle went down the road. I don't think that method would be the least expensive.
The other option you mention is to acquire the components yourself and send them to the smith. I would suppose that the rifle smith could get a bit of a better deal on components than an individual, but I feel that bit of an extra margin should go to the smith. Some of the smiths here bill very conservatively and deserve every break they can get.
My current build, components being piled up at Kirby's shop as I post, is a pretty much total LRH.com rifle. The action, barrel and scope base came from Earl in Florida. The stock came from TMR. Rings and one of these days the scope came/will come from BJ/Lerch. I think I still need an ADL trigger guard. Havent seen any posted lately and may have to resort to Sinclair or some one.
The only downside of this method is you have to get what is for sale. I would rather have a Lilja bbl than the Pac Nor but I doubt I'll be able to notice the difference, if there is a difference.
Regardless of the components, I would suppose that all of the top of the line, are pretty much equal, the secret is the rifle smith. I think you'll find the best of the best lurking around here.