You're missing my point. All those factors are real, but they set the unit economics of taxi service, which in turn sets the baseline for Uber/Lyft pricing.

So if the market price for taxi service in a city is X, already accounting for all those factors, Uber/Lyft should be able to deliver the same or better service for (say) 0.9X, again accounting for the factors but adding in efficiency gains from bypassing parasitical taxi medallion owners, not needing dedicated vehicles, having much easier ordering, etc. There will be some variance in how big that factor is (eg. NYC's $1 million medallions gave Uber a really juicy margin to exploit), but overall, if a city can sustain taxi service, it should be able to sustain Uber/Lyft too.