theoretically a cheap bike should only be marginally worse than an expensive one, and that is usually the case with claris/sora and altus/alivio (8, 9 spd) bikes vs more expensive ones. That's a basic bar of quality. They're perfectly good for most uses.
To understand why -really- cheap bikes are so bad you have to understand chinklogic. A consumer might have an idea of a basic standard for a bike, and the manufacturer might communicate that basic standard, which seems reasonable, and it's how western consumer protection laws work, but really, the only descriptor of an item that matters in china is the price and an excessively cheap bike is describing itself as garbage. It is unreasonable to expect it to be good. It's not just going to be heavier and clunkier, it's going to be fucked out of the box. Misaligned frame, way too tight bearings, if you repack the bearings with good grease they will still never be smooth because they're so poor quality, so much flex and slop in the brakes that they'll always default to squeeling, bolts that strip out if you look at them wrong, absolutely garbage built wheels with fucked tension that are very difficult to true to any reasonable level. They're basically projects from new and require a decent amount of skilled labour to fix to a save or reasonable level, which is, not worth it and in many ways, impossible.
They're not on the continuum of quality, they're below a line which makes them categorically different, more akin to scooting along on a stolen shopping trolley or a nigerian wooded wheel scooter than a 20th century machine.
