Nope. It's the other way around. You got a deal.
Auto Zone sells these new for about $35. Most mechanics charge about $100 per hour labor. It would take a mechanic about 1/2 hour to change the part. So $35 for the part and $50 for the labor comes to $85. You were charged $80.
By the way, many shops will charge a set amount of time for a job no matter how long the mechanic actually took to do the work. This is usually more time than most mechanics need. If the book says it takes an hour to change the part you are charged one hour labor, even if the mechanic did the work in 30 minutes.
So many shops would have charged you more labor for this job.
