Take a look here
for an example.
I pick my parts up at the local distributor in South San Francisco. My web vendor is 3,000 miles away. I pay no delivery cost. 99% of the time they have the part in stock so I can start a job with the confidence of knowing I can complete it with a new part if something breaks (which it does, from time to time, on my 1983 300SD!).
Oh! yes, I almost forgot. I usually park next to the Mercedes Benz of San Francisco parts truck which is picking its parts up at the same time.