I don't know used prices, but they sell for $500 new. New, there's no price difference between the .58 and the .54, so I don't know if .58 would have any added value on the used market. I'd say go with general used T/C Hawken prices as your guide. You can probably get an idea by checking the ones sold on firearms auction sites, or maybe some kind soul will have a Blue Book handy.