Most fuel lines can be repaired for no less than $120 dollars. If the fuel line has to be replaced entirely, the cost depends greatly on whether the mechanic has to drop the car's fuel tank to replace the lines. If so, this can add an additional $400 or $500.
Some car owners may have fuel lines that are extraordinarily rusty, and repairing or replacing the fuel lines may disrupt the brake lines which are often nearby. In these instances, it may further drive repair or replacement costs up because the car owner must now purchase new fuel lines and new brake lines simultaneously.