Mighty Muffler

I arrived with a code P0421 a catalyst failure and left $500.00 lighter with a code P0421. He replaced a flex pipe $150.00, fuel injection/ throttle body clean and tune-up (plugs and wires $225.00). I came here asking for a catalytic converter. He said the other people didn't know what they were talking about and I just need a good cleaning! After coming back two times he finally agreed to sell me a catalytic converter installed for $800.00 more. When a came back the second time I accused him of only having $100.00 and two hours in the project, and he said that he had invested $123.63 or a 400% mark-up for 2 hours of work.