Fraud in the public transport network of Paris costs a whopping €366 million a year, or €1 million each day, according to new figures from France's Court of Auditors - the Cour des Comptes.
The auditors revealed that 8.9 percent of passengers weren't paying the correct fare (or indeed weren't paying at all), which compares with a rate of 1 to 2 percent in cities like London, New York, and Brussels.
Valérie Pécresse, the head of the Ile-de-France region, said the figures were "scandalous".
In launching a new "anti-fraud" campaign on Tuesday, Pécresse said that it was time "to change this idea that people can cheat the system with impunity".
Indeed, you may have already seen posters across Paris and in the Metro showing people with dragons on their shoulders, together with text like: "Scammers, the rules have changed for YOU".
While the choice of dragons has been mocked in French social media, it appears that the transport heads are taking the matter very seriously indeed.
The signs refer to a new set of rules put in place to try and earn back some of the money that these fare evaders are costing Paris transport chiefs RATP, train operator SNCF, and region's transport authority Stif.
The measures include new powers for ticket checkers to detain fare evaders for up to four hours if they can't provide ID. Those who don't hang around can face up to two months in prison and a fine of €7,500.
Giving false information to ticket checkers can result in two months in prison and a fine of €3,750.
Repeat offenders (cheating the system five times a year or more) can face up to six months in prison and a fine of €7,500.
And a new law prohibits people from "reporting on the presence of a ticket checker on board", an act that now comes with a the risk of two months in prison and a fine of €3,750.
The campaign aims to win back an annual €20 million for the RATP and €10 million for SNCF.
On the suburban Transilien line, free riders cost the service €63 million a year, according to the line's director.
He said that of the 3 million daily commuters, 220,000 weren't paying the proper ticket.
The line is training up 500 new ticket controllers, and giving ticket-checking authority to those working in the stations.
To prove how easy it was to fare-dodge in Paris, Le Parisien newspaper reported that three of its journalists rode the network for a full week at peak times without paying and never got caught once.
Each of them tried different techniques - one jumped the turnstiles, another asked fellow passengers to let them pass through on one card, and the third perfected the act of feigning business while walking past ticket controllers.