re: Is anyone here dumb enough to think the Wall costs $12.5M a mile?

Having hired contractors to build stuff, I have a simple rule. If a contractor says something is black, I'm certain it's white.

Never believe contractors, always have them sign lien waivers. As a general rule, they've never seen a bill they intend to pay, or a job they can bid accuratlery, or track and account for properly while it is in process.

Funny business, most aren't smart enough to know whether they're even making money until the job is complete, and many don't even know at that point.

Hopefully this helps you understand why I wouldn't ask a contractor anything.