Probably between 5-800$depending on how pretty she is. That is a commercial Luger. The pitting in the bore gives you some negotiating room as it means it may have been used during the war when corrosive ammo was used, and then not well cleaned afterward. The new grips don't add a thing to the value. Take off the grips and see if there are any rust pitts under the grip panels - that should drop the price more. Check to see if the firing pin works - take a thin pencil with you, one that will fit down a 9mm bore - cock the pistol, drop the pencil in eraser first and fire it and the pencil should shoot clear of the barrel. The action should lock open with an empty magazine - if not, either the holdopen spring (flat spring) is weak or needs replacement.
Do not dry-fire Luger pistols on empty chambers - you will bust your firing pin faster than if you were dry-firing a CZ-52 - use a fired case.
Beyond that there is little to do until you are ready to fire the pistol. I woulad advocate getting a take-down manual and replace the springs with a kit from Wolff.
If you purchase this pistol do not fire +P ammunition - it is too hot for the pistol. The pistol is designed to fire 9mm ball, 124-5 grain, at 1100'/sec or less, and that is hot enough for a P-08 Luger. HTH. Mikey.