And, of course, there is a fee to be paid to the CAA to be an examiner. How does an examiner earn that back? Not from the one hour's flying if done with another instructor/s!
I think you need to separate the revalidation from normal class examining. A revalidation examiner does not pay anything for the authorisation. A FE/CRE pays and they recover this through doing skill tests or as is the case for some of us it is use in the normal course of work for crew currency and is covered by the employer.
Guidance from the CAA is that there should be no charge for signing certificate of experiences as it is a paperwork exercise. For the five minutes it takes to check the licence, logbook and sign an SRG1119 this is not an unreasonable position I think.
There is a lot of myth and rubbish around this. I know for example a friend who is in the CI was made to do another 1 hour with the CFI because he was told the hour with the Instructor had to be in the last 90 days even though I had 10 hours of dual with me 6 months earlier and was then charged £28 on top of this to have his licence signed.