You pay $100 a year because you think it makes you a pro. The service that you get for that is on your invoice, if you were not CPS you would have been billed $3,145.51, had you chosen to do the repair you would have been billed $2,487.27, CPS membership would have saved you $658.24.
Why do they charge to open your camera? My guess would be because every time anybody ever took an out of focus or incorrectly exposed image they would blame Canon and send their camera in for "free" estimates. I get five free cleans and checks a year, but no free estimates on damaged gear.
Even for non CPS the phone staff have a discretionary 15% they can work with too, it pays to be nice to the telephone staff.