You would think paddle weight is not very important right? You would think your weight, your board's weight, your technique, and your board's hydrodynamic characteristics are more important than the weight of your paddle. In cycling (road racing and to a lesser extent time trial and triathlon) people talk about "rotating weight" being more critical than static weight. That is to say, the weight of your wheels are more important than the weight of your frame. Think about the weight of your paddle compared to you and your board. For me, it's less than one percent of the total package weight (rider, board, paddle) but because that weight is being moved forward and across your body many times (40-50?) per minute, the weight of your paddle and the energy required to move it, really starts to add up.
Take a look at this brilliant article by Bill Babcock of Ke Nalu paddles to learn more about this. If you haven't read his other articles, be sure to check them out, they're fascinating!