Extra stops are charged according to whether or not if the stop is en-route to a pickup/destination. Stops are priced according to locations, extra time, distances, and urban settings.
There is a $7 charge for each additional stop made during a trip in the same zone en-route to the destination, plus added time and distance to the trip.
The extra stops fee is higher if the stop is not en-route to the destination, and outside of the immediate pickup or destination zone. Those zones vary depending on locations, extra time, distances, urban settings, tolls, or any other incurred fees.