The cost to replace a fuel pump varies depending on the car and auto repair shop used, but the bill will most likely be hundreds of dollars. Fuel pumps need regular replacement because the amount of strain an old one puts on a vehicle.
The job of a fuel pump is to take fuel from the fuel tank and deliver it to the engine. Driving around constantly on low fuel will make the fuel pump work harder and require more frequent replacements. It is relatively easy to remove a fuel tank and replace it with a new one, but it is best to use the services of an experienced professional who knows how to properly install it.