Recently took eurostar to paris nord station. unknowingly got into a "gypsy" cab, it had a roof taxi sign and a meter.
cabby did not turn on meter and when we got to hotel asked what did his "boss"" say the fare would be. his boss was the young man who directed us the cab, which was in a line of cabs outside the door marked, "taxis".
i told him his boss did not mention the fare, he suggested 45 e's which i felt was way to high. gave him 40 e's. asked the hotel folks who felt the ride should have been around 20e's.
steves guide book indicated that the taxis in paris are all regulated. be aware that there are gypsy type cabs that look like real cabs buy take advantage on travelers.
Sounds like you were in the real taxi line but got a rogue driver. Not turning the meter on is a giveaway that something's wrong. The taxi number should be displayed on the left back window of the cab along with an official government phone number to report problems. Sorry this happened to you as 99+% of the Paris drivers follow the rules. Thank you for the warning.
There was another thread recently about this same issue altho I can't come up with the correct search terms to find it. He thought he was at an official taxi rank, but had followed a person out a side door to were taxis were waiting.
Use Uber where possible!!
Have no plans to use Uber ever.