I kinda agree with Jman. The amount of money you'd save on say a high end ball when you consider paying for the drilling anyways isn't that much. Personally I'm lucky that the pro shop on the naval base here doesn't have an out the door price above $210 on any ball so it'd cost more for me buy one from bowlingball.com and pay to have it drilled. But even then, say a high end ball at your local shop is $240, even if that shop charges $50 to drill, you'd be spending say $220 to order the ball, wait a week, then pay to have it drilled. Might as well spend the extra $20, and the most you'd have to wait is a day. I doubt many people are buying balls online then having them drilled, at least with new model.
I'd imagine most of the ball buying on the internet is discontinued balls. I doubt bowlingball.com or any site is gonna list a discontinued ball as a best seller.
As for pyramid, as far as I know that's the only way to buy them. I haven't seen any in stores. But most people see a cheap priced new ball and wanna give it a try, especially guys who drill their own stuff. I wouldn't doubt at all that they're stuff is the most popular stuff, mostly cuz you can buy other stuff elsewhere