This is addressed at the bottom of the linked page:

  What does it cost?
  Groupon Store: There's no upfront cost. For promoted deals you get 70% of each Groupon sold. For non-promoted deals you get 90% of each Groupon.

  Deal of the Day: No upfront fee, you keep 50% of each Groupon sold.

Was it widely known that Groupon's cut on deal of the day is 50%? I thought there was some to-do a few weeks back about them wanting 100% of Groupon proceeds for some cafe.