Re: SATA on a pi is possible
Horrific bandwidth, far less than USB 2.0 so not worth bothering with.
The Broadcom SoC has very few "high bandwidth" interfaces - the camera interface, LVDS, HDMI, SD/MMC and USB.
They'd need to switch over to a different SoC that has PCIe or SATA as well for SATA to be worthwhile.
There are quite a few sub $50 single board computers that have that, albeit much harder to buy.