I think dotman laid it out pretty clear but think about it like this from my involvement with RMEF. A gun company, let's say named Timber, will give the RMEF a gun or guns at a discounted rate. Let's say they will give a rifle called the Fountain Descent to RMEF at a 20% price break. Since the Fountain Descent usually retails for $1000, the RMEF has to fork over $800 for the gun.
Now, the RMEF can choose to have the gun in an auction, or other banquet event or membership drive. Auctions don't get much anymore because everyone can look up the value of the gun and nobody would pay over $1000 for it at auction so the RMEF would only make $200 for conservation.
Next up would be some other banquet event. A simple example would be a limited draw. Let's say the RMEF sells 20 entries at $100 a piece. Not too bad as you have a 1 in 20 chance of winning a $1000 rifle and it only costs $100 to enter. With 20 paid entrants, the RMEF just made $1200 for conservation. This model is great but has limited reach as it can only happen once a year at a banquet.
Finally, the RMEF wants to do a membership driver. let's say their lifetime membership costs $500. They combine the lifetime membership with the Fountain Crescent rifle and sell the package for $1350. The RMEF gets a $500 membership plus a bonus $50 to use locally or donate to the mothership. The buyer gets a lifetime membership and Fountain Peasant for $150 cheaper than what it would have cost to purchase separately. And finally, Timber, the gun company probably gets some sore of deduction (Just guessing here) but they also get their product out in the hands of hunters and their name associated with the RMEF and conservation.
Now I will say this regarding the BHA deal, it's hard to really say what kind of deal is actually in play because they never state what the cost of the lifetime membership is without the added goodies. Looking up a couple things it looks like it's roughly $750 over the retail cost of the item/reward/goodie. My guess would be it's more towards $1K and you are getting $250 off the retail of the reward or something like that. To be honest, I don't know what a lifetime membership really gets you in "value" over just a yearly or 3-year membership. Since a yearly individual membership is $25, a $1k lifetime membership is equivalent to 40 years worth of annual memberships. I know it's not about the bottom dollar but it is a bit interesting if you break it down.
Oh, and to the OP, it's easy, I'd get a rifle...I think...maybe the 1911....pretty sure...don't really need another Cimarron...!#@!#@