Once you start spending that kind of money you're better off going with a working Honda or Yamaha.
I could be wrong on that. I can imagine the enthusiast who is willing to spend comparable money for something of comparable quality, yet something that is individual to himself. Something he built himself. Many of us do exactly the same thing with these cheaper components, of course.
But it's risky. Aside from expense one might well spend an awful lot of time getting the thing built and, maybe, spending an awful lot of time keeping it in good working condition.
And then, after all that, he might find that replacement parts are hard to come by.