/you play: (/opponent plays R/P/S)
Rock (0, -6, +3) = worst overall step payout (-3)
Paper (+6, 0, -6) = neutral overall step payout (0)
Scissors (-3, +6, 0) = best overall step payout (+3)
But then if both players know that playing Scissors is the "optimal" play, then one of them playing Rock to beat Scissors (at least once) will be the actual best play, until the other player catches on, the regular RPS takes place, ignoring the uneven step payout.