Currently, Ruger 10/22s are priced at $279.99 at Sportsman's Warehouse for the blued barrel, wood or synthetic stock. You mention an extra barrel, do you know what barrels come with the rifle? The value would be increased with a SS barrel, a threaded barrel, or a Volquartsen barrel or parts. The model and brand of optics could also make it worth $300.
I would be interested of I knew more about this rifle.