I am traveling to Paris for my vacation beginning of October. Before that, I had done some research and there is few type of transportation from Charles de Gaulle (CDG) airport to Paris city. You may refer the list of transportation to/from cdg airport here. The cheapest way that I found is using Easybus or Bus 350 & 351 operate by RATP

When I touch down CDG airport, I try to book Easybus online, but the website show no ticket available at that moment. My alternative option will be Bus 351 to Nation which near to the apartment I rent.

I went to RATP office at CDG airport to purchase T+ ticket. (Some where terminal 2 if I not mistaken). To buy 10 ticket in bulk, you require to walk into RATP ticket office because automated machine only can purchase 1 T+ ticket, not able to buy 10 T+ ticket in machine. (Note that 1 ticket cost 1.90 euros, buy  10 ticket at 14.50 euros)

When you boarding Bus 351, you had 3 option to pay.

  1. you may use 3 ticket you purchase (1.90 euros each) at the automated machine
  2. you may use 3 ticket from the 10 ticket you purchase at RATP office (each cost 1.45 euros), this is the cheapest option.
  3. or purchase 3 ticket from the driver cost 6 euros

As my experience, the bus is not much passenger from airport, but along the route, it had more passenger coming up and end up the bus is full of passenger. You might need to take care your luggage and belonging.