Bettors may view different gambles either as substitutes or complements. Assuming that the grand prize is the main driver of the demand for multi-prize lottery bets, this paper presents a theory of lottery sales maximization considering possible complementarity or substitutability among different lottery gambles offered by a single operator. Optimal payout ratios are derived accounting not only for interrelation among games but also for their relative popularity. The new profit optimization rule is then applied to a dataset of two Greek lotteries.