When I was in high school my dad was given a house with the condition that we tear it down and clear the lot. He took it to get the lumber. We ended up with a LOT of usable wood among other things. There was no labor cost because it was myself, two sisters and four brothers along with dad who tore it down. Pulling out old nails is one hell of a chore. The scrap lumber that we couldn’t use was given to my high school for it’s annual bonfire.
I don’t ever want to do that again.
A froend gave me some 20 foot 2x6’s he took from the garage he tore down. I didn’t think I would ever get all of those old nails out.
The longer boards are worth the effort, not sure the shorter ones are.
I'm with you-- I helped to tear down an old barn once and my main job was pulling nails, thousands of nails.