He says the value drops a lot because I didn't have them in a gun safe with humidity control. I inspect them weekly for any sign of rust and I haven't seen anything.
I've known people like this. Funny how such people are all about denigrating a seller's wares before they buy and then how they turn around later and brag about the "steal" they got on this "awesome stuff".
If he can get a brand ndw AK for that price, then he should do what everybody else would do...go out and buy that brand new AK for that price. But he can't, and therefore he won't.
If he says the value drops a lot because of the way you store your gun, then he don't know a thing about what ACTUALLY drives the price of a gun with respect to care. What makes or breaks a gun with respect to condition is the actual condition of the gun itself, not how it was stored. If it is in pristine, like-new condition because you've carefully maintained it that way, it doesn't matter if it was stored in a humidity controlled safe or in a gun rack over the headboard of your bed.
I can understand your desire to establish a fair price range. Personally, I think your spot on with respect to what you might consider a "fair" price.
Ultimately, what is fair is what both the buyer and the seller are happy with. But there is "fair" and there is "fair".
If you want the most you can get for these, then research what they're going for on various sites and base your selling price range on that information in an effort to get the most for your guns.
If I were selling to a friend, then personally I'd take a look at what I paid for the gun, the condition it was in, the current market value, and then I'd set a price that I considered to be fair and which would probably be a bit less than I'd accept from someone else.
If I bought a gun for $200, it was in great shape, and the going market was $250, then I wouldn't have a problem selling it to a friend for $200. He gets a good deal (below market price), I get a good deal (I get what I originally paid for it) and we're both happy.
If I bought a gun for $200, it was in great shape, and the going market was $750, then my price would likely be higher. Maybe $500 or $600. I get a good deal in terms of profit, he gets a good deal in terms of below market value.
If I bought a gun for $200, and the going market was $250, and I thought my friend could do with a really good break based on his personal circumstances, I may sell for $50...or even gift it to him.
It's all a personal judgement thing.
Personally, your "friend" seems to be trying to take advantage of you...and that doesn't sound like much of a friend to me.