What is fair price for plug replacement? 2005 Prius

probably around $250. are you gonna do the water pump and coolant?

 

"Fair" price is SUBJECTIVE. Labor rates and parts price MARK-UP are all over the place. You need to call shops and ask what they charge for the work you want done.

Yourmechanic.com is probably a good starting point; physical shops prices will likely be higher. This company has a smart business model: ondemand (by appointment) certified auto mechanics come to your home/business to perform limited work you specify. You can even supply the parts! I'm sure if they seem something that is an issue, they will let you know and you can choose to have repaired or not.

 

My local mechanic charges $80 an hour. Dealer is $ 140 an hour,.

When I changed my plugs it’s pretty labor intensive. Lots of stuff to take apart. I was at it all day.

I checked the park plug wells with a borescope before I pulled the plugs and found oil pooled in cylinder 3 and 4 which meant The valve cover gasket needed to be replaced so had to go back in there again later.
Leaking gasket causing pooling of oil is pretty common and may be the cause of any misfire.

I also changed the pcv valve and found the 2 hoses that go from the valve cover to the throttle body had cracked ends so they needed to be replaced so pulling the top of the engine aprt on high mileage car will sometimes reveal lots more issues than you were even aware of so keep that in mind if you think it’s going to be s hard and fixed price.
Oh and it may even need simple throttle body clean too. That’s an hour labor right there. And may need a fan belt. That’s another hour ...you get my point.