Cheap cables are just that, cheap. Really in the long run they don't save you any money at all because of inferior cable leading to shorts and lost tone. So if you can, stay away from those.

Are high qualty cables worth it?

They are made of thicker outside material which leads to lower microphonics and quieter operation. The connectors are more solid and less likely to fail. The inside cable which is very important is better quality. That better quality leads to less resistance and better tone, it allows all your tone from the guitar to get to the amp! This also makes all your effects sound even better, simply put all the tone is getting thru the cable instead of the resistence eating it up.

Evidence Audio Lyric HG and Melody cables I believe are the best with the most sonic clarity and Paul Reed Smith cable is excellent too. There are a few others but these are my faves. If you are serious about your tone and have spent some good money on your rig then don't skimp here, otherwise you are just robbing yourself of better tone with poor cables!