If you travel frequently then a Carnet is a great way to save money.
Carnet 6
Carnet 6 gives you 6 one-way trips for the price of 5. Valid for 12 months from date of purchase. Valid in either direction. Tickets transferable.
Carnet 12
The Carnet 12 gives you 12 one-way trips for the price of 9. Valid for 12 months from date of purchase. Valid in either direction. Tickets transferable.