I have a different explanation for this, Jamshid. You may correct me if I'm wrong.
As long as
well-paid modifies a noun, it is hyphenated. Just like in " a
laid-back person", for instance.
'good-paid' or
'good-paying' must be usual errors of informal English vernacular. "
good" modifies a verb, so it has to be an adverb - but 'good' is never an adverb, '
well' is.
Listen to this:
'How are you? - I'm feeling good' or
'I'm good, with or without you',
'It's a very good done job, I must say'. I cringe whenever I hear 'good' used as an adverb. I often heard such phrases while in Virginia. Spoken E is relaxed, free from boundaries and constraints. In writing, however, there are rules - "well" is the adverb, and should replace "good" in the aforementioned expressions.
Was my explanation well? Or good?

(just kidding)