Just put six new tires on the sprinter after 80K. First time I've seen why the 6 wheeled 3500 is different than the 2500s which have 4 tires. Though we occasionally haul a 35 ft. towable lift behind, other than that the extra capacity of this vehicle hasn't been necessary.
To your point Paul, I did due diligence, my dealer (mercedes) offered me a full set at their price $1600.00 (for 6), I was able to buy them from discount tire up the street (1/2 mile from home) for about $1,000.00 with free checkups and rotations on them, same tires.
Now when I went looking I of course saw all kinds of yelp reviews and others slamming everyone from pep boys to discount tire and big o and others, so in the end service wise I think you get lucky or you don't, but ultimately I agree that the tire thing is a wide range of pricing out there.
***
My disclaimer is when I buy anything I look online to compare any price I'm getting locally, I will never stop doing that, even if the online folks have to start taxing people. As Mtncat found, cheaper price online and even with shipping (which is often free) you often can't beat going online for most goods.
I'd also put in a disclaimer that while folks always say it is good to buy local, I've seen a lack of interest in selling me product often, or basically a lack of customer service or pleasantness in selling product from many local supply chains and such, so why bother.
Case in point, I just bought a cement mixer for our new venture that I happened to notice Home Depot was testing as a new product line. I tried to get them to special order me the 12 cubic foot size with electric motor from the company so I could use my HD account with deferred interest for 24 months.
Two different pro desks got all my info said they'd call me back no matter what they ran into and I got nothing.
So I ordered it from Toolfetch.com in NY state, it is shipping freight to me in NM (free freight) and they had a $100.00 coupon code for these mixers for the month so I paid $600.00 less than I would have paid from any other vendor including my local Home Depot.
***
For me money is too tight to not shop around, look for coupons or discounts and be wise with it. Love what I do, but do intend to have the option someday to retire!

Justin