When it comes to selling old, or used firearms..it comes down to..profits vs Time.
Unless you are selling a rare model, war trophy, special edition, low serial number, hard to find, etc firearm, the longer you are willing to wait, your chances of getting more money for it increases.
If you want it gone fast..for whatever reason, you have to expect to get far less than retail. If you are not in a hurry, places like Gunbroker are the better choice.
If you like to gamble, a live auction is the most fun, but the most risk as well.
If you are not doing a consignment, and selling to someone like Cabelas...expect to take a bath. It's just capitalism, it's not personal. Need cash fast? It will cost you.
Just how it is.