In my personal experience, Discount tire offers better customer service than Costco Tire center. The generally great costco customer service doesn't carry over to their tire center. They are overly cautious about liability issues, like not selling you 1 tire, not installing your own tires, not selling you tire sizes or tires of a specific spec. They go by the book and won't use brains.
Toyota decided to equip my car with z rated tires out of factory, even though my car is not a sports car. Costco refuses to install anything that is below z rating. Most shops where the reps are allowed to use their brains will laugh at installing z rated tires on my car.
When costco had michelins on sale, I printed out the online prices and took it to discount tire. They gladly matched the price and installed the tires I wanted. Little did they know that I had no option of getting these tires for my car from costco in the first place.