They used to say academics was less production/pay and private practice was high stress/high comp. The gap has narrowed because the academy is demanding much more, lots of rads are just nonacademic employees of the university behemoth working a generic job, and the labor shortage means hospitals/universities need to pay more to compete in the job market.
Perhaps counterintuitively, strong private practice in the face of the labor shortage is one of the factors driving up academic compensation.