Weight affects power consumption when riding up and down slopes and by scaling the rolling resistance. The weight difference between very lightweight (expensive) equipment and standard equipment is relatively small when compared to the total weight of the bicycle and rider system. Also, the aerodynamic resistance is generally much higher than the rolling resistance and energy lost to elevation gain. Therefore the power savings from using ultralight gear is correspondingly small. Thus it makes much more sense to invest time and money in reducing your CDA than shaving grams of bike weight!