there are so few SP-1s in that condition, and enough collectors and hype that someone will pay something exorbitant for it.. I'd like to see a benchmark like this for Boss pedals. $900 is worth it if someone is willing to pay...
I would have liked to know the serial number of this one. It's a 6 digit number and black thumb screw so it must be a late one. The pocket dictionary must have been added later. That's Vol 5 and it's from 1988 so it couldn't possibly have come with the pedal originally.