Flat fare between Charles de Gaulle airport and any address in Paris: €56 to the Right Bank, €65 to the Left Bank, day and night. Your driver tracks your flight and waits at arrivals with a name sign.
Charles de Gaulle (Roissy) is about 30 km north-east of Paris. The fare depends only on which bank of the Seine your address is on.
Same price day and night, luggage and tolls included.
The RER B stops at every station and can be crowded. A taxi is simpler with luggage, in a group, early in the morning or late at night.