If you have a costco membership, they're generally the cheapest. if not, i've never seen anyone get close to Discount tire, whether you've had bad experiences there or not, it's still the cheapest out there, generally.

you're not really doing an apples to apples comparison. 30k warranty--what does that mean? is it a performance tire with softer rubber? is it a crap tire that's just not going to last? are you going into these places saying "i need tires for my nameless AWD sedan" or are you giving them any input on what you want?