A quick note on my experience; Back in 2011 I donated a bunch of firearms to the NRA Foundation as my health was presenting issues; the NRA took the guns, auctioned them off, and the money (a) provides an annuity for me and my wife until we both pass, then (b) goes to whatever NRA program you designate; in my case, the NRA ranges. The annuity is not large, but a welcome addition to our retirement.
The NRA used the Greg Martin Company in San Francisco for the auction; Frankly, they were a bunch of crooks, hammered guns down to shills in the audience for fractions of what they were worth; I saw some of my guns on the internet within a week! Thankfully, we were informed the NRA does not use Greg Martin anymore, which is a good thing, and despite that, we have made out financially OK, although I may live to age 90 just to beat the odds!
I know a lot of folks are not huge fans of the NRA, but along with the 2nd Amendment Foundation, they are the only folks working to protect our 2nd Amendment rights. For example, the Board members of our local gun club were sued by a neighbor who objected to the noise (he built his mansion downrange of a shooting range that had been on site since 1968). We won, of course, but the NRA and the 2nd Amendment Foundation worked hard and spent money to protect the club, and by extension, us Board members. Just a thought.