Totally anecdotal: while travelling abroad I tried to order an Uber with my regular account and card. The process went well up to the point where I could see the price but then failed because my card was not accepted for some reason. Immediately switched to "cash" and the price displayed went down. The original price was 30% higher. The same evening I repeated the same steps with another fare and got the same outcome.

I'm not sure if this was a coincidence, some local policy regarding paying cash vs. card, or Uber doing something shady. But I asked all my friends to compare the price with the driver (or pay cash, although this may be less convenient) if they ever use Uber. I've read articles before that Uber was showing the driver a lower price than the customer in order to give the driver a lower cut. If this is the case then it wouldn't work when paying cash.