I was under the impression that the TCs were really close? Though I've never seen one IRL. Too bad.
Anyway, I've spent a lot on my franken MBW 5513 with gen more or less everything and I don't think I'd do it again. Even with all the money, work and parts I have in it I'd never mistake it for a gen in a million years.
If you have the skills and tools to do most of you're own work it's ok, but otherwise you're very dependent on the rep community for repair work, mods etc and also resale as mentioned earlier.
If you lose your high end rep/franken or it gets stolen you can kiss all your money good bye. No insurance is going to help you.
And you're also running the risk of being called a cheap, fake, poser, white trash, POS no matter how much you spent on your rep, or how much you love your hobby.
I've never met anyone who likes, respects or even accept rep/fake stuff.
So, in my opinion reps can be great and fun, but once you go with expensive versions and mods it can end up costing more than it's worth. It all depends on yourself really.