Re: Whats are preseason tickets running this year?
Your best bet is to check the secondary markets:
Stubhub or Ebay
You can get a feel for the going prices for various areas of the stadium for the game you're looking to attend.
The Cowboys game will probably command a steeper price than other pre-season games simply because of the intense interest both from Texan and Cowboy fans. That said, I would still be reluctant to pay over face value for pre-season games.