What is the avarage cost to repair the timing belt on 2005 Scion xB

My sons car stalled on the freeway and had to be towed. It was taken to Sears and he was told that they did not replace the timing belt. He took it to our family mechanic and was told the same. Why?

Asked by for the 2005 Scion xB
according to our price estimator, you have a chain which gets replaced at engine overhaul.