You should be able to set a certain fare for the current distance algorithm which is used in game. With this system, there will be more competition between taxi drivers resulting in lower prices for customers, and more customers for drivers due to it being cheaper.
The current price for a taxi is
too damn high resulting in little to no competition and the same is said for customers.
There should also be a command /getfare [id], which when typed shows you the current fare(price) that a driver is offering.
On top of this, taxis should be able to be purchased which would enable players to even create taxi companies. These four models should be put up for sale.

P.S Could it be possible to have an overlay of maybe a fare meter, which shows you the fare, like
this maybe?