Pitch slider seen better days

my pioneer 1000's mk3 are just over a year old and the pitch sliders are playing up. I took them to a shop and they said the copper track inside them is worn away. Im being charged £160 to have them replaced, I was told the warranty doesnt cover wear and tear.

Is this a normal problem? Am i being ripped off? I paid it out of desparation cos I have a big gig coming up and have to practice. Let me know

thanks, josh