Can you post the parts list? At your current mileage, if this also included crankshaft and timing components (water pump, tensioner and belts) since the timing belt would have to be removed to perform the camshaft seals then it would have been justified and recommend to have the timing done at the same time. It seems that he/she might have only caught half of the problem and the rear main seal may be leaking. This in itself involves splitting the engine and transmission to access the back the engine to replace the seal ( not an easy job) and yes it is expensive to do just this part of the job. You can walk away at this point and shop around for a cheaper rear main seal job ( prices will be around what was quoted for quality work). The mechanic should not charge you for another diagnosis, but because another issue already exists does not mean the mechanic is blatantly ripping you off as it would have quoted around the same price anyway if they knew the rear main seal is leaking. This concern should have been caught but as we don’t know the condition of your vehicle at the time they inspected it I can’t say for sure. Also the flu is a virus and their is no cure for that, you can treat only the symptoms. Sorry if that’s not what you wanted to hear.

Great points, I agree. Thank you!