I'd check the date and offer a little over half as well... if they're within a couple years old. Anything older and I'd pass, I live is SC and the sun it brutal on tires here unless you keep your vehicle garage and keep the tires wiped down... but who does that on a DD?
A co-worker is a friend with a Michelin Employee (Michelin owns BFG now) I got a set of all terrains for about $250 less than retail. They were literally days old when I got them. They smelled so good