I didn't see this so I hope it's not a duplicate post
Effective March 1st they have a flat fare to and from the airports. In addition, they have capped the amount the cab can charge you if you call for a cab
https://www.service-public.fr/professionnels-entreprises/actualites/A10124
Google Translate of above webpage below
Taxis: flat rates between Paris and airports from March 2016
Published November 5, 2015 - Directorate of Legal and Administrative Information (Prime Minister)
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From 1 March 2016, flat rates are established for direct strokes of Paris taxis between Paris and Roissy-Charles de Gaulle and Orly (2-way).
The price is fixed and must be determined before the delivery, according to the following maximum amounts:
• between the airport of Paris - Charles de Gaulle and Paris right bank: € 50
• between the airport of Paris - Charles de Gaulle and Paris left bank: € 55
• between Paris-Orly Airport and Paris right bank: € 35
• between Paris-Orly Airport and Paris left bank: € 30
Similarly, as from 1 March 2016, the supplement for booking taxis in Paris becomes fixed, regardless of the distance traveled by the taxi before the treatment (approach stroke):
• immediate booking: € 4
• advance booking: € 7
Moreover, for all races Parisian taxis, care supplements for animals or luggage are deleted; one additional passenger surcharge can be applied from a fifth occupant, including a child.