really, that has all been done except the steel brakes. Just as one obvious example, the '70s Schwinn Varsity had really nice one-piece cranks and everything else on the bike was high quality but as cheap as possible. And it retailed for well over $500 in today's dollars. You would have to go single speed and cut a lot of corners to get to $100. I think the Walmart fixed gear Ronald McDonald bike is what you would get. It's not bicycle negligence, but you can do a lot better for not all that much money.

I was riding to school back in the late '70s and a guy in front of me took the sharp turn onto the bike path a little wide. His forks collapsed sideways and tacoed his front wheel. Typical department store bike.