In transportation business major costs are vehicle depreciation/maintenance/consumables (fuel, insurance, tires, etc), wages and you can include domain specific expenses (insurance, driver health chek-ups).

  * You can't reduce DS expenses. You can offload them to drivers, but that will still be reflected in prices
  * You can reduce wage cost by eliminating administrative load by having tools (apps, backends) do the job. Considering the size of Uber they are just transfering wages from operators to engineers.
  * You can't reduce wehicle depreciation. You can reduce maintenance costs by having own workshop. Taxi companies might have that, for Uber that would be next to impossible due to practical reasons. You can reduce operating costs by buying fuel/insurance/etc in bulk. Agin, easy for cabs, difficult for Uber (not impossible though).

The only place I see Uber can compete is having innovative algorithms route the cars by adjusting for projected demand. Unless they have huge army of dedicated drivers, drivers driving for multiple companies kind of defeats that advantage. currently Uber does compete by exploiting legal frameworks and not labeling their drivers as professionals and their service as transportation. This is not a major factor in operating costs though.