Maintenance cost vs. value

What is your question?

My Cayenne S is due for 40,000 mile major maintenance which includes oil change,filter element change, fluid checks,changing spark plugs, and a brake fluid flush. The balance of the work is visual inspection. The dealer wants @$1,300 for the maintenance. My local shop (whom I trust after 15 years) can do it for a fraction. I know it is a high performance vehicle, but its still just maintenance work. Is there something I am missing?