How much will it cost to repair a gas leak?

Any fuel leak is not good, actually it probably started a little while ago, but none the less , Locate the source, fuel filter,metal/rubber fuel lines or a tank leak . Have someone to do a visual and smell test under the hood and vehicle, use vehicle safety.Also you can have a pressure test done. The cost depends on where the leak is, and what a person may want to charge for their time. All the above parts are underneath the vehicle, fuel pressure regulator, injectors, fuel rails , are under the hood.The fuel lines metal or rubber are not that expensive, repairing the tank varies. Have vehicle check by a quality shop or knowledgable tech, first before spending a lot of money, let me know what you find, thanks, but have checked immediately. May be small (smile) No smoking/flames around the vehicle. Also have you started putting more gas in , in the last few weeks? Your fuel pump is in the tank, so it is not what you smell, it is a leak, quite possibly a fuel line.