That’s kind of the different way of looking at it. Where people diverge, if you will.
The opportunity cost of keeping it is whatever you could have had for selling/trading it.
How much of a hassle it is depends on the type of firearm, your state, and your personal preference. It’s really not much hassle. I’ll tell you what’s a hassle…selling your old car.
It’s certainly less work to keep your guns, that’s for sure. 
I think I was unclearly trying to make two points at once.
After the ATF knocks on your door you can refer them to the FFL transfer record to prove that the firearm was no longer in your possession.
And they should not have a record of that transaction until you point them to the dealer where you sold the firearm. But given it has been revealed that the ATF has a database with around 1 billion firearm related transaction records in it I suspect they are somehow getting their hands on a whole bunch of information they aren’t supposed to have and may already know the transfer took place.
Came to that very conclusion brother.
These (3) firearms are just good basic guns,
A HiPoint (never fired) (7) mags, single stack,
A Ruger P-89 (7) mags, bluing worn on slide, old reliable.
A PSA Dagger FDE (10) mags one of the first versions, non red dot,
Really good shape (fired 500+rounds through her)…
Wouldn’t get much for them, would trust them to save my life.
HiPoint a new replacement for a second hand C9 that Broke dead so
they unbelievably replaced it for free yet to me but it’s kinda suspect.
Wouldn’t let these be my beloved Sisters
‘If her life depended on it’ pieces but @ $130 (HiPoint) what would I get? not much.
(3) hard working guns, way down my list for carry/ Insurgent disposal.
I’ll keep them all. I spread them around the Casa. Some neighbor, decent folk
died (6) months ago and his wife sold me (3) lock boxes and a Medium size safe
so I spread the guns around already. Never know when you might be caught in the Can or something right?
I’m really lucky. I know that. NOT complaining at all. Just thought somebody else might need
a piece to defend themselves. but current climate I would worry i’d get Bit badly if I sold them/gave 'em away. I handed over a couple of family shot guns helped ‘watch over’ some Battered Woman in the past, They were family owned (no paper trail) taught them how to defend themselves a little better. But
Cautious these days about ‘Helping’ out in this case. If I felt the NEED to arm someone up, I 'd go with them to an LGS and help them $$$ buy their own gun (in their name). Provided they weren’t a CRIM. 
Still a bit burned these days by my BEST Friend gave me (2) old Revolvers a 1930 something Colt and an equally old Smith (stamped Colorado PD) Before they moved to texas last month his wife demanded them back. No sweat I said, HERE, Cleaned them up for him, gave him the 100 rounds I bought for them
(had no .38’s in my care so what the hell right?—nice gesture I thought) he had no ammo for them so they would be paperweights. (Then went out and got that M-206 cutie for Sis !) Life’s Funny Haa Ha!
Yeah, each bathroom has a gun. Every bed has a shotgun under it as well as 9mm Sigs next to my bedside. The wife has S&W M&P Shield. Let’s see guns are in picture frames around the house and in our frontroom and familyroom I have shelves that open at the base and both have three handguns in them. Each has a 38 revolver, 9mm 20 rounds, as well as a 22mag with 30 rounds!!!
My wife, our 4 boys and our daughter all know where all the firearms are as well. Everyone is currently grown and out of the house.
Heck, my oldest son can shoot very well with both hands. Started right handed but thought, hmmm, I bat left handed, so he started shooting left handed. Wouldn’t you known it, he actually had better groupings left handed. He writes with his right hand. Who would have thunk it.
Now we all practice with both hands. You never know what may happen to your strong hand.
Same, Same here Bill,
I ‘almost’ crossed that line in her sand when I hung my older Anderson on the center post in-between our rides in the garage until she asked what was in an old military bag hanging next to it and I said ‘(10) 30 rounds mags!’ and to my surprise she laughed and just shook her head. I may be a little Worldly and been around the world a bit but I can honestly say without hesitation :
“I will NEVER understand Women folk!” “NEVER” and my world righted greatly once I understood this.
(again a movie reference) I think she would indeed draw the line like in the flick “Dogs of War” when Chris Walken opens his 'fridge for a can of beer there is an old what looks like a beretta on the metal shelf! There would be some push back on that front! 