I don't see any difference between this and the way they report most stories. I love the way they calculate average wages: They don't point out the hundred+ people making over a million a year, or people like McCartney reputed to be making a million a day through various business deals and royalties, and I don't think he is alone.
I don't think the BBC (or any other medium for that matter) actually calculate average wages. That would be an impossible task.
They simply report what the government (in the shape of the Office of National Statistics) publishes..