Well, since I volunteer for the RMEF,,, I get to see a lot of "special" guns. Generally, unless they are issued with a factory verified "different" model number, and have something special not normally available, they usually only command premiums by people associated with that group, and them wanting that peticular gun.
Quite often,,,, RMEF, NWTF, NRA, DU, RGS, etc all get guns from manufacturers and then have them embellished and they sell or raffle them at events. Some are quite nice,,,, others,,, so-so.