https://www.vice.com/en/article/mechanics-ask-walmart-major-...
https://old.reddit.com/r/MTB/comments/z2d5h5/walmart_bike_un...
So for $118 you get a really poor quality bike that you probably can't repair. Or perhaps you'll end up with one that's just unsafe. $400–500 is probably a reasonable price point, but that'll get you something that's adequate at best. Heavy, clunky, and unpleasant to ride.
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.
That ‘Heavy, clunky’ bit is key.
A good bike is addictive to ride. It’s like a sharp knife through butter.