It rarely pops up for the DIY/MYOG community. Seattle Fabrics used to carry it at one point and it was also in the $25+/yd price range. I highly doubt there is a cheaper source for it that's easily located. When you look at the price of dryskin clothing, they usually are very expensive and most companies have gone and switched to proprietary fabrics for their softshells.
Also the Dryskin Extreme that Shelby has is different from normal Dryskin. It has a coolmax lining for wicking purposes which further bumps up the price (but yeah 50 euros/yd is A LOT).
Rocky Woods has Schoeller Dynamic for $17/yd. It's not as bomber as dryskin but it's well reviewed.