I needed a new heater core. Erwin quoted $950 total to install a new OEM replacement, including shop fees and taxes. After I dropped it off, they called and said they had a NAPA (aftermarket) unit. I knew that the OEM unit was $329 and the NAPA unit was $66.49. After I prompted them, they gave me a revised quote of $710, which reasonably reflected the difference in price for the part, so I gave the OK. After the job was done, my bill was $808 ($98 more than quoted). On the invoice, they showed the job was $729 including parts, but then they added shop fees and taxes on top of that. I guess they were going to get their money one way or another. Never assume their revised estimate is a total.