I had a similar experience this week. Shopping for 2 new front tires for Maybelline I was on tire rack, Walmart, and a few other sites, as well as comparing to local quotes. Walmart was $10 per tire less than Tire Rack so I had them shipped to my local store for free.
When I went to get them installed, the girl at the desk offered me the full cafeteria menu of install options. I went with mount, balance, and road hazard. I convinced them to swap the valve stems for free and discount the install since the tires can't be rotated.
Rule 1 from Purchasing, You don't get what you don't ask for.
Rule 2, Don't take a no from someone who isn't authorized to say yes.
I'm loving my new (to me) daily driver.