KBB and NADA means almost nothing in the Viper market (for a limited production vehicle). Actual retail is based on market value (what other Vipers are selling for considering mileage, condition, etc.). If he's interested in a stock, one owner, pristine Commemorative Edition (only 100 made) with 6,500 miles, send me a PM.Kelly blue book is always way low on Vipers. NADA is closer. Black Mamba is a pretty desireable model, only 200 ever made. White Mamba is even more desireable by many. I would guess 47 to 48 is not a bad deal. 52 is on the high side, but not crazy.