The impact of substantial increases in the size of expected laboratory payoffs on subjects' behavior is examined. Consistent with a model of asymmetric risk aversion, subjects in first price auctions consistently bid above the risk-neutral Nash prediction. It has been argued that this is due to low opportunity cost of deviating from the risk-neutral bid. The opportunity cost and payoff levels are increased by factors of zero, one, 5, 10, and 20 from the normal levels generating payoffs up to $250 for risk-neutral subjects. An insignificant increase in the slope of individual bid functions is observed. Only 4 of 154 subject observations are consistent with risk-preferring behavior. After controlling for experience the observations across individual subjects show that: 1. individuals bid higher (more risk averse) as the payoff conversion rate increases, and 2. decision error declines as the payoff conversion rate increases.