How does ScotRail's "Friends Fare" actually work?

[Dirty_Mac]

I saw this on ScotRail's website but could not for the life of me figure out how to actually book it. BRFares suggests it's £63 (Edinburgh–Inverness) for up to 4 adults, but doesn't that seem too cheap? On the other hand, if it's per person, then it's barely less expensive than an off-peak return, and will almost definitely cost more than any advance fares, especially given that it's booked trains only.

 

[Paul Kelly]

The price covers all passengers. I tried searching at a few different times and it does not look like Scotrail have set any availability for the fare, and since it's an advance it maybe means it is not purchasable in reality.