If they are so invisible not to matter, then why aren't they higher already? Why would Uber lose money if they didn't feel like they have to?
If Uber increases from $7.51 to $7.96 you might not see the difference in your head, but then if for example lyft is offering $7.80 for the same ride, whats more likely for you to choose?
I think they'd be very careful with increasing prices and wait their competitors to increase prices first so they can follow up, or else they might run themselvs out of business.