If someone is a bad player who loses I doubt they would take $100 to the $.5/$1 tables at pokerstars...

I see many very poor players at the "standard" buy-in of $40, and that is often a sign in itself they are weak.

Those who buy in at $20 (the min) are simply jokers waiting to be had. They can't even get action or push anyone from a pot and often limp out most their money before going all in. TBH these people are barely worth the $20 because they take up a seat that somone much more "giving" could occupy.