Table schema:
CREATE TABLE trained_in (physician VARCHAR, treatment VARCHAR); CREATE TABLE procedures (cost INTEGER, code VARCHAR); CREATE TABLE physician (employeeid VARCHAR, name VARCHAR)

Question: 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"