Are unused U.S. stamps from the past worth anything more than face value these days? (Please see details.)

I don’t mean stamps from way back in the past like the 1930’s or 40’s. But I do mean unused stamps from, say, the late 1970’s or 80’s, before the arrival of self-stick style stamps, the kind that you had to lick before putting them on the envelope. The stamps are unused, un-canceled.