$35 for one plug?! Let's see, thats 6 plugs, plus $20 for wires...$230 in parts alone. Then you have to add labor, the cut the mechanic recieved trying to get the back plugs off, the burn his assistand recieved trying to hold the motor steady by gripping the exhaust pipes, cleanup for the oil that "started leaking" out the oil pan plug, new oil for the car, new mop to clean the oil mess up, Diagnostic for the new "sputter" the motor "just started" making, excessive repair to the fuel rail that is causing the "sputter", and you can have your car back in 35 minutes, along with the discounted bill for $1300.
-OR-
Do it myself for ~$45, and have the car running great in 15 minutes. The increase in gas mileage along will pay for the repairs over a period of one month, and I won't have to do it again for an entire year.
Need I say more?