It isn't the case they are more expensive than taxi's where I am. I take it now that isn't the case everywhere. And even in in the SF area I don't believe that taxi's would be cheaper if you lived slightly out of the core areas and had to call one to drive out to you.
I am also still extremely skeptical they contribute to higher prices though. If Uber and Lyft did not exist I believe (just a theory) that taxi prices would be much higher.
Perhaps someone who lives in a city where ubers are banned could state if taxi prices have grown over the years.