I don't see what the problem is - if someone wants to spend £80 getting a professional opinion of their riding position then its their choice, same as if they decided to buy a new saddle for £80 or a new seatpost, etc.
Yes you can try to work it out yourself, but not everyone has different stem lengths, top tube lengths and seat tube angles, etc.
If you find that you have an ache in the small of you back, your knee, or you left eyebrow, its not always an intuitive step to work out that your seat is slightly too far forward or your stem is 10mm too long.
If you've asked around and no-one else can help out then sometimes carrying out a mechanical assessment of you on your bike is the only way.
And no, I haven't had one, I much prefer to keep tinkering with the set up of my bike every year....