Depends on how much time you have to visit Paris and how early or late your return flight is. If you want to stay at the airport, try ibis or Novotel in Roissypole Gare RER. There is a free and direct driverless train (CDGVAL) that takes you there from all airport terminals.

If you want to go or stay in town, take the public bus to Opera-Garnier. You will find several hotels in that area but will set up back around $250 plus.

Be aware that August is vacation month in France and some of the restaurants/stores will be closed.