When gun values are discussed, unless the heavy hitters here weigh in, I do a search on gunbroker.com to get a relative value.
I did a few searches (on the ones I like
):
Remington 760:
Remington model 760 Gamemaster 30-06 : Pump Action Rifles at GunBroker.com
Remington 1100:
Remington 1100 12 ga For Sale
Walther:
Walther PPK/S stainless .380 For Sale
Not a perfect method by any means, but it at least gets you in the realm. Good luck. There are some nice Spoonage on the list.