Uber does minute-to-minute dynamic pricing, so any one ride isn't indicative of the actual cost. It may well be more expensive, but one or two ride anecdotes would not prove it.

Was this before UberX? Checking just now Uber quotes about the same as a taxi for UberX in Paris. The premium Uber (called "Berline" in Paris) is 60% more, so matches your experience.

The rentals I'm referring to are all UberX.

https://www.uber.com/fare-estimate/

https://www.taxifarefinder.com/main.php?city=Paris-France

There's been a few times where the yellow cab flat rate to JFK was cheaper than Uber in NYC as well.

I've been using Uber and similar apps for years mostly in Europe and Asia and 80+% of the time the price would be substantially cheaper than taxis (often 50% cheaper in places like London). They use dynamic pricing though based on supply/demand so it is very possible to have higher price than taxi based on parameters (i.e. if you booked a ride in central Paris during rush hour the price would spike up). But from my experience you cannot use those anecdotes because if you use Uber a lot (like hundreds of rides) you will statistically see they they are cheaper in big majority of cases.