Not the first I've heard of it by any means. Although not common it is becoming more so and in my opinion, it is becoming a better check as 170 examiners begin to devote more time to the check.
Think of it like a business and if you say it isn't then you need a reality check!
An authorised 170 examiner, has to apply for his status and basically pay to renew it. They are pretty much just one rung down the ladder from an examiner and thus have a large amount of experience and expertise. The school often generally pays someone with this experience more to retain them. Experienced staff demand higher wages or they move on....
You are paying for their experience, skill set and judgement skills.