Exchange members are subject to self employment taxes. (i.e. an additional 16.5% that retail traders don't pay). If a membership is only going to save you an extra grand or two per month it's not really worth it. YM is a hard contract to trade size in on a consistent "all day" basis. I'm only a 10-30 lot index trader and I find the number of partials to be a pain in the ass in YM. Hence unless I'm spreading YM against NQ I rarely trade it. Obviously the time to buy a seat was before the mutualization of the CBOT and CME.