When you take YOUR gun in to a GUN STORE, it's really not at all about "worth." Of course your gun has worth, value, etc etc.
Simply put, that gun dealer is in business. He's not there simply because he had nothing better to do that day... He's got a lease, electric bills, employees, and a lot of investment in stock.
Folks definitely get blown away when they hear a number on their gun being sold or traded to a gun dealer. It's a business. They can't keep the door to the joint open giving you what you might think your gun is "worth" or even what it actually is worth.
If you are absolutely certain that it's "worth" some certain dollar value -- then prove it. And there is only one way to prove it.
Find someone to pay you that number in cash. When you have accomplished that, then you've proven that "worth" was correct. Until you can get some guy's cash in your hand, you are merely talking about some number that is a simply a conjured up figure from a few different sources.
As for going in to the gun store and getting offended... well, that's part of the business. You'll get offended and you'll either get over it or you won't. In the mean time, that dealer will take in a number of guns that month and he will profit on that venture. He's able to do that because he's got cash, some knowledge and also a store front that you don't have. People come to him when they need or want to move a gun along and he will get many of them in that way and it's worth it, even if a few folks get offended.