On average, a spark plug replacement at a mechanic will cost between $115 and $200.
Cost of parts: Spark plugs cost between $5 and $20 each, depending on the type of plug needed. Since you need as many plugs as there are cylinders in your engine, that means you’re looking at four to eight plugs, or anywhere between $20 and $160.
Cost of labor: This is not a particularly labored procedure, so expect to pay for one or two hours of labor at approximately $30 per hour. Note that labor costs change dramatically from one zip code to the next.