I can't say with any authority, but much of the high price is due to the high cost of the base imagery from GetMapping. Unlike the US and even Austrailia, where orthophotos are either public domain or only attract nominal fees, the European government mentality is that *everything* must not only pay its own way, but also make a profit.
As to why it's last, that's easy. It was only 2009 that photography of Scotland was completed, and even now, the colour-matching of all the photograps to a standard acceptable for FS is still ongoing. Just getting enough cloud-free days (in the right places) to