As far as the BOM, you're asking the wrong guy, but someone upthread mentioned that it'd have to run off the usb, which is one of the reasons why you'd have to wonder what the point really is.

One very real cost would be the increase in size to the PCB and everyone's cases. Plus, we could talk about how external sata just isn't very good as a user experience, while usb is.

I haven't shopped for really cheap storage hardware lately but I question that there's really an area where sata could be a cost win.

> And keep in mind that nowadays the price point of a fully kitted raspberry pi is already close to 100$.

There's a really wide variance there, though - you can get a lot done for under $50.