Paying isn't depended on a number of seats, but how long the destination is, At least that's how taxi driver job works in my country.
This is what I mean:
For example: I have a fare and I go from Alderney to MGS, that will pay me 600$.
But if I have two fares from Alderney to MGS, I should be able to /acceptfare both, and then both pay 300$ -> 600$ total.
And if I have 3 fares, same story, all three pay 200$ and 600$ will be the total paid to the taxi driver.
So the money gets divided and you can accept more fares at once.