Sometimes people just consider era for era without the intent to offend.
I think getting into the scarity of a card on a trading card site is a bit irrelevent when you talk about trading with or for 1980's cards form anywhere, I started collecting in 1979, so I saw plenty of all of those cards at shops and stores even back then. my dad paid $10 for an entire 1978 OPC set. Using this logic presented in this topic i guess I need to offer my 1952 Red back Allie Reynolds(3 for trade) for a 1981 OPC Dave Concepcion, but I think we would all agree that's probably not a good trade for me, but I will give it a shot, maybe that will get me the last few 81 OPCs I need for my set.
Or perhaps another trade floated, 1953 High Numbers for a Heritage Josh Donaldson card(1 for trade).
Sometimes trades just involve an offer that looks to help one person complete their set in exchange for helping another person get cards they want, i have accumulated a lot of cards, so I am glad to move some for some stuff I am looking for. I have enjoyed this community a lot over the last year, getting almost 500 trades done, but I do find some trading logic a bit weird, but to each their own I guess, that's what the trade blocking list is for.