Of course, there is a part of the "freelance teacher" concept that I believe can and should be cultivated in the United States. If the focus of education is on accumulation of knowledge and mastery of skills, rather than a naive emphasis on seat time, grade levels, and Carnegie units, then much could be made of a private enterprise industry where teachers impart skills in knowledge in the most accessible and effective formats. Specifically, this could be considered an a la carte education system in which students and parents access what they want and need. This could be appealing to many in the homeschooling and unschooling movements. It may not be a bad thing for students to access school on a hourly or unit basis, rather than a year. For example, I know of parents who would willingly homeschool their children in all but a few areas. And there's probably nothing wrong with that.
So, I don't know about a system of hagwon with the best teachers earning millions, but the United States could certainly adapt a more freelance approach to education.