Tire prices are determined by the type of tire you're looking to buy as well as the brand. Also, my Costco tire center mainly stocks Michelin, Bridgestone and BF Goodrich. They may have to order Goodyear tires. You should contact the tire center.
It'll depend on your vehicle type. But if you are not a member of Costco then you cannot make any purchase from there.
Thanks! Your answer is awaiting moderation.