Not sure unless those years had weak strikes and maybe they are harder to find in the higher grades? The mintages arent anything siginificantly different than other years so it's not that.
My hobby: collecting real money 1 copper cent or nickel at a time.
I just checked my "coin market" price guide. It shows $12.50 for an MS-65 82-P and also $80 for an ms-65 Full Strike. Kind of supports Daviscfad's answer.