Yes, the prices were the main reason why I went ahead and built it. I ran out of "excuses" long ago.
As for lapping the upper, I had one other upper that had been lapped by my buddy Dtech, and it was a good shooter. This one is also a good shooter.
I can't attest that lapping one makes them inherently better, but it sure doesn't hurt to ensure that the surfaces are as flat as they can be either. I mainly did it to make the mating surface between the bolt ears and the barrel extension so everything would be as inline as possible, more than making sure the barrel wasn't canted because with modern CNC machines, we all know that isn't much of an issue.
I've known you long enough that I'd let you borrow my lapping tool/compound any time you want it, just say the word.