A gaming system comprises a wager input device for receiving at least one wager and at least one display for displaying a randomly selected outcome of a wagering game. The at least one display further displays an expected value indicator. The gaming system further comprises a controller operative to (i) add a portion of the at least one wager to an actual turnover, (ii) randomly select a trigger amount from a range of available trigger amounts, (iii) update the expected value indicator to indicate the actual turnover relative to the range, and (iv) award a mystery prize in response to the actual turnover becoming equal to or greater than the trigger amount.