ok I am thinking out loud here so bear with me. First I looked at the parts on World of Triumph parts. And your dealer price is in there not that it aint a fleecing
Triumph Motorcycles | triumph-select-model-part | Triumph Parts | Triumph Clothing | Triumph Accessories | Triumph Bike Rocket III - Classic - Roadster | ThrottlesInjectors amp Fuel Rail
Anyway I am assuming it is the part number 27 which does not include the fuel rail just the two hoses the short steel line that raps around the back of the tank and the banjo fitting. So My question is if that steel line is corroded? I would take a look at it. Because if it is not and the rubber hose is leaking I would wonder why since they would have to crimp the hose clamp band to the fuel rail why can't they just replace the two rubber hoses and crimp new hose clamp/bands on them. That pipe is coated for corrosion inhibiting I find it hard to believe it is bad unless you live near the salt water and yet I still have not hear of Florida Rockets suffering from that and they do report the corrosion problems on the bike.
Like I said I am just thinking out loud.
Off to play pool Retirement is hard on a feller