Yes, the $118 bike is not going to be much fun, and may be assembled dangerously. It's still a bike, though, and a little TLC and attention to assembly before riding will prevent a significant number of problems. Even the reddit thread you linked just required some screw tightening and replacement of a derailleur -- and a cheap Shimano derailleur is $20 from my local bike store.
Even if we completely discount the $118 bike (plus a $20 part), though...
> $400–500 is probably a reasonable price point
This is a far cry from "much under a grand". Yes, it will be heavy and clunky, but it will function in all of the ways that it is important for a bike to function.