What are the first name and last name of the professionals who have done treatment with cost below average?
SELECT DISTINCT T1.first_name ,  T1.last_name FROM Professionals AS T1 JOIN Treatments AS T2 WHERE cost_of_treatment  <  ( SELECT avg(cost_of_treatment) FROM Treatments )
SELECT DISTINCT T1.first_name ,  T1.last_name FROM Professionals AS T1 JOIN Treatments AS T2 WHERE cost_of_treatment  <  ( SELECT avg(cost_of_treatment) FROM Treatments )
[{'first_name': 'Taryn', 'last_name': 'Braun'}, {'first_name': 'Jayson', 'last_name': 'Ullrich'}, {'first_name': 'Olaf', 'last_name': 'Watsica'}, {'first_name': 'Vernice', 'last_name': 'Tillman'}, {'first_name': 'Danny', 'last_name': 'Considine'}, {'first_name': 'Ruben', 'last_name': "O'Reilly"}, {'first_name': 'Velva', 'last_name': 'Hayes'}, {'first_name': 'Karley', 'last_name': 'Hyatt'}, {'first_name': 'Monte', 'last_name': 'Kshlerin'}, {'first_name': 'Domenica', 'last_name': 'Jacobs'}, {'first_name': 'Brady', 'last_name': 'Pouros'}, {'first_name': 'Winfield', 'last_name': 'Christiansen'}, {'first_name': 'Ericka', 'last_name': 'Murazik'}, {'first_name': 'Sigurd', 'last_name': 'Frami'}, {'first_name': 'Lesly', 'last_name': 'Walter'}]