When BB30 came out it was pretty light, and the SI cranks were the schnizzle. They're probably still one of the lighter cranks overall, although I'm not keen on their SISL set up. I don't know of anyone who pays retail on them, I wonder if they've come under the "Cannondale R2000" pricing policy. In that situation I think about 80% of those bikes were employee purchases so Cannondale priced them to be sold at employee prices, which meant that MSRP was higher than buying a frameset, Dura Ace group, and the rest of the build kit, I think MSRP was about $1k over retail, for a $5k bike, give or take. I know I haven't bought any of my SI cranks at anywhere near retail. I imagine most come on bikes and are sold as take offs.

It seems that non-BB30 cranks have caught up with both rigidity and, to a certain extent, weight. Shimano is super impressive.