A useful calculation for psychology professionals is to work on 1000 paid for sessions in a 40 week year and per session costs then equate to annual salaries if multiplied by 1000.  So $100 dollars per session becomes earnings of &100,000

Haas-Wilson, D. (1991).  The impact of vendorship legislation and interprofessional competition in the market for social workers' services: International Journal of Law and Psychiatry Vol 14(4) 1991, 305-314. 

Kovess, V., & Buras-Eisenberg, A. (1983).  Influence of the way of payment on the demand of psychotherapy: Comparison between clients of psychoanalysts, conventional psychiatrists and a free center in the "Region Parisienne."  Social Psychiatry Vol 18(1) Jan 1983, 13-24.