I know $5,000 sounds like a lot of money. But it's barely scratching the surface to get a reasonably good franken. Mine is based on a MQ case (yes he was a major PITA to work with) and runs an ETA 2846 movement.
In rough terms:
Case $1,000
Crystal $700 - $1,000 (gen T17 Superdome)
Bezel $350
Insert $300 (rep) $2,000 (MKIII gen)
Crown $800
Tube $200
Band $250 (rep Yuki) $2,500 (gen)
Dial $1,000 (MQ)
Hands $300 (rep) $1,000 (gen)
You're already into it for $6,700 plus and that's with a dial any expert can pick out at arm's length and no movement. Throw in a gen ETA 2846 for $300 and then wrestle with having your $1,000 case machined for the correct stem height. Bear in mind, are you SURE you're sticking with the MQ dial and its thickness? Or will you eventually move to a Dark Lord dial and its thickness, if you can find one? They're not the same and your machined case won't accommodate both with a correct stem height. The difference is small, but are you going to cut the feet off a $1,000 dial and use dots? Now start looking for flat gilt hands to match the dial. A member here just finished a project to create nearly perfect hands, and might still have some for sale for the ETA. Otherwise you're into it another $1,000 for good ones. But then the gen spec hands won't fit the cannon pinion on an ETA movement unless you broach/stake the hell out of them, then they rub the minutes hand.
So you get it all put together and tweaked, 3 or 4 or 5 trips to different modders to get it tweaked JUST right. Then you start watching for a Dark Lord dial. Yes they're worth it, they're made on gen plates with gen pads and gen techniques. Mine is. For all intents and purposes they are gen dials. Once you find one, you send it off to the best modder you can find and pray he'll be able to modify the case to accept the dial, then you wrestle with cutting the feet off a gen 6538 dial to mate to the ETA movement. Now we're getting into the realm of ethics. Or you find someone with the skill to drill your ETA main plate to accept the dial feet, which is ridiculously easy to screw up. Now you're servicing your movement again, and you realize... now my dial/movement depth is wrong for how I had the case machined to accept the ETA plus MQ dial with its feet cut off and dial dots. Your new stem height is too high. DAMN. Now what do you do?!
So eventually, after a few expensive mistakes down rabbit holes, you wind up with an aesthetically perfect Big Crown running an ETA movement, put together the right way, and it runs great. It's 7 or 8 years later, and wow does it sparkle on your wrist. But now you realize it looks too "new". This watch is supposed to be 60 years old and it obviously isn't. So now do you start to age your creation? Are you willing to use it HARD and acquire real patina? Do you beat it up to gather artificial damage? Or do you put it on a shelf as a perfect, shiny bauble because nobody will believe a 60 year old watch can look that pristine?
The question is, who do you want to please? You, or other people? Welcome to the world of franken Big Crowns.