They have a very hard limit on how many you can buy.
So if you want more than two, you can't buy more than two. With PC Richard, it was the same price as Amazon, but I could get a bunch. Same deal with Best Buy. They have the same price as Amazon, but you can buy three and then potentially go to another Best Buy and buy another three if you wanted while they're on sale for this price before they're discontinued.
Be careful with Xfinity. I just changed my internet plan and they disabled one of my two cablecards without me asking. Now they are refusing to activate it again because they no longer provide support. At least it is a reminder of why I'm moving away from all their services.