Reminds me of the lady that recently had two breasts removed and then was told they goofed and she didn't ever have cancer. Oops. Sorry, but the tests got mixed up.

Does anyone think the hospital purposely goofed so they could do the surgery and collect the $?

Same thing here. Probably just a human error. The mechanic noticed the engine running on one cylinder, assumed the older engine needed rebuilding and then estimated costs. They probably didn't purposely misdiagnose the engine to screw you out of money. The mechanic just goofed.

My point? For serious medical or mechanical repairs, always get a second and third opinion. Too many people(mechanics included) assume they know what is wrong before doing a thorough examination.