I pay around $9. 00 for Premium Blue. I haven't priced Premium Blue 2000 (synthetic blend). I also get mine at a local NAPA store (Festus, MO).
I run it around 7,500 miles per oil change. This is with little to no towing. I have sent in oil samples, and based on them I could put more miles on it, but I don't think I want to push it to far.