There are exclusive contracts everywhere. If one company wants to pay another company to be the exclusive outlet for their product (which is a marketing tactic), then they are more than welcome to do so. It's about as far from an antitrust issue as you can get. Antitrust is when you buy out or merge with your competition, thereby eliminating them so you don't have anything keeping your prices in check (which is what XM/Sirius did).
The price of ST isn't Directv's fault either, it's thanks to the NFL.
The price of ST isn't Directv's fault either, it's thanks to the NFL.