Hi Ben,
I have not been able to determine if the one-way RER fare from CDG to downtown Paris has increased during the Olympics. I can find the in-town fare increase info, but not the single trip from CDG. In all the trip planners I still see 11.8e but saw a post on another forum that said it's up to 16e. Tx
1 answer
The single-trip price for the CDG to Paris airport fare/ticket hasn't increased and remains at 11.80€. The 16€ price is for the Roissybus CDG airport bus, which has increased a bit from its usual 14.50€ price.
You can see the Olympics price changes in effect on this page at RATP.