CREATE TABLE trained_in (physician VARCHAR(255), treatment VARCHAR(255)); CREATE TABLE procedures (cost INTEGER, code VARCHAR(255)); CREATE TABLE physician (employeeid VARCHAR(255), name VARCHAR(255))
What is the average cost of procedures that physician John Wen was trained in?
    
SQL: SELECT AVG(T3.cost) FROM physician AS T1 JOIN trained_in AS T2 ON T1.employeeid = T2.physician JOIN procedures AS T3 ON T3.code = T2.treatment WHERE T1.name = "John Wen"