For them to charge a fee after the fact because they feel “used” is inappropriate. If a representative for a major brand intends to charge a fee for the fitting, that 100% needs to be disclosed up front.
I think it’s possible that the trainer (who is likely getting a commission or sponsorship related to #s of saddle sales) and the rep (also getting a commission) were counting their commission dollars before they materialized.
For trainers who are sponsored by various saddle brands, there often is a minimum number of saddles that that trainer is expected to facilitate the sale of within their barn each year. So, it is possible that your failure to purchase a new saddle through the rep is an issue WRT your trainer maintaining their own sponsorship. Because your trainer is taking the saddle rep’s side here, I am suspicious that (and I could be totally wrong here) this after the fact fee relates to something more than just the saddle fitter being annoyed that they did an extra fitting.
FWIW, I understand it that a saddle fitter might feel “used” if they made a specific time consuming trip to a barn, did a fitting, and it turned out the person had no intention of buying and simply wanted to get the specs of the saddle that would fit them best so they could shop for a used one on the internet. In that case, the salesperson has several options within their control. They can 1) understand the bigger picture, which is that it is a chance to build their network at a particular barn and there is a possibility that the customer (or one of their friends who might be looking on) could end up buying a new saddle at some point in the future, or 2) offer exactly such a service for a reasonable, discussed up front fee, or 3) do a fitting but not necessarily turn over a list of the specs to the customer at the end of the fitting. Those are all proper, perfectly businesslike options.
I just want to reiterate that having an appointment with a rep is NOT an obligation to buy, and that charging a fee after the fact is a shady business practice no matter what business you are in.