When I left after year 3 I was making $42k a year. While that is a good salary, I didn't see myself able to support a family on that salary. So I left, went to grad school, and now work in industry.
It may sound vain or materialistic, but had I made $80k, I likely never would have left teaching. I really enjoyed being in the classroom.
In order to get great teachers, you don't necessarily need to make teaching lucrative, but you do need to be able to provide a salary that enables the teacher to support a family.