exploitation of arts professionals

It is extraordinary though wholly familiar that arts professionals are expected to deliver high level services for nothing or next to nothing. Enthusiasm and commitment are exploited by those commissioning services. The most recent example is a podcast I was asked to record by the National Gallery in connection with the Leonardo show. I was asked to record items on the anatomical drawings, one of which, the vertical section of a man's head, provides a wonderful entry into Leonardo's ideas about seeing, thinking, imagination, memory etc. I negotiated the fee up to a grand £100! This was absolutely their "top fee". The gallery was unable to fix the recording at a date when I was due to be in London, and I therefore had to make the journey specially. On claiming expenses, I was told that they were not part of the deal.  Given average mileage rates for travelling from Oxfordshire, I end up with  £14.20 for something that consumed at least 4 hours of my time. I asked,  "would you expect to employ an accountant or solicitor for this kind of money?" adding that " I am a professional speaker, writer, broadcaster now! There's something very wrong with the priorities here."
The podcast was being made by a company called Antenna, but all my correspondence was with the gallery. They have said they will claim expenses from Antenna, but to date .... no fee, no expenses.
And this in connection with a show that is sold out.
This is just one small incident in the broader picture of exploitation of artists, curators, writers, speakers and administrators. This occurs as a matter of habit even in connection with events that involve large budgets to cover substantial fees for other professionals, such as designers, publicists and the deliverers of other services.