I'll stick my neck out a bit and venture a guess at doing this today with no "inside deals"....
How about $3000-4000 for the base gun (Fox 20ga ejector in good shape), $1000-1500 for the metal sculpting/filing/tang work/polishing for engraving, $1000-2000 for a stock blank, $2000-3500 for the stock making/finishing, and maybe (I'm not well versed on engraving) $3000-5000 for that scratching in the picture depending on who does it, tack on another $500-700 in blueing, casehardening, etc., then another few hundred or so in shipping.