^^^
like he said...
also, as was intimated, Cannondale's frames are not inexpensive as compared to a whole bike. They are in the bike business, not the frame selling business.
if you are doing an upgrade with Cannondale's frame upgrade program, that will be different. In other words, you already own a Cannondale and want to go to a nicer frame. It's a good way to get and keep customers.