False Engine Light Diagnosis and incorrect part quoted

Bad bad bad. I brought in my car with an engine light on and i was told that my ECU (a very expensive part) needs to be changed. Went to a different workshop and it was found that another component was the actual problem. So i basically paid for a false diagnosis at VW Hoopers because i had to re diagnose the car. They quoted the most expensive part so as to make easy money, i would have had the same problem with a new ECU. Sad.