70K would have been a bit much, but low to mid 50's isn't out of line for what the car was. I can buy an M3 for 65k. Add to that 10K in mods to 75K and have a nice car, that looks like most other BMW's. They also have issues with spinning the crank hub and destroying motors. Other option is something like a Cayman S. Your looking at 65+ for a good one. C6 Z06 is the closest, but not a fan of big cars, and the interior isn't for me.
I've been contemplating an extreme FD street build. I think you have to think of it as a custom car build and forget the chassis. It could be an Rx7, vintage car, etc..., if you are customizing most everything pick a shape you like and start from there. I think that's what Eric did on that car. Yes it was missing AC and PS, but that's a pretty easy fix. I've added up everything and I can get to 90K+ really quick. Now that's with a dry sumped LS7, infinity box wiring, custom interior, 8.8, chem dipped chassis, tig welded stainless exhaust, etc..., but this stuff adds up quick, especially if you refuse to cut corners. Most builds I see I would strip down to the bare chassis, and start over from there. They're just not in the the league of what I would call an extreme build. Absolutely nothing wrong with that, it's just a different sort of thing. It sounds like Eric came out swings so to speak which is unfortunate. If the car had remained in the for sale section I might have seen it.