I buy from Costco whenever possible. Usually the bundles include an extra controllers and cables for the same cost. Plus they have a hassle free return policy. If you notice, the MGS4 bundle includes an additional DS3 and HDMI cable for the same cost as the standard bundle, a good deal if you ask me.
Bottom line is Costco sells a lot of everything. They are the fourth largest retailer in the US and is one of the leaders in selling consumer electronics.