We have run into several varaitions. Most often; The customer (commercial cust's) will have materials on-site for us to install.
With one recent job they shipped the materials directly to us to receive, transport to the site and install. We told them there would be a labor charge for receiving the materials, a transportation charge for reloading the stuff onto our truck and xporting it to the job. Not a lot of materials, but a van full.
The customer response; "Oh, you're going to charge us for that?" I was surprised an explantion was necessary! They didn't argue the charge, just seemed a little surprised we would be charging for our time. I hope this isn't a trend because I don't like it!