My view is that if Uber has already displayed a confirmed fare for the trip, the driver generally should not demand an additional payment outside the app simply because they want to charge more. The passenger should normally pay the fare shown or charged through Uber.
There can be legitimate exceptions, such as certain tolls, airport fees, parking fees, route changes, or other charges that Uber allows to be added.
However, those should be legitimate and explainable charges, not simply because the driver believes the Uber price is too low and therefore asks the passenger to pay extra. Its insanely stupid.
So if the driver was saying, βUber says the fare is 4,000, but I want 10,000, so you need to pay me the difference directly,β I would not consider that reasonable without a legitimate Uber authorized reason for the additional amount.
Overall, my observation is that the passenger has a reasonable basis for questioning the extra charge if the Uber app clearly showed the original fare and there was no legitimate additional charge explained by the driver.