Err, I sharpen my own 1/2" teeth with a 3/4 hp bench grinder, I use the normal grey wheel to clear away the steel under the tip and the green wheel for the tungsten carbide... it's easy... but with the Rayco Superteeth I just silversolder new tips on.
Maybe it is cheaper in your area but Every sharpening service I ever found cost nearly the same as new teeth. Your best options probably are: A. Buy new teeth from someone like Leonardi Manufacturing or B. sharpen them yourself with a bench grinder and either a green wheel or diamond wheel