I am not a vet, but I totally agree with you. You spend years training to do what you do, only to have people baulk at you charging for your 'expertise'.
I remember James Herriot saying once that the vets stand out as the ones who charge, and I do think some of the problem is that humans have the NHS. We simply don't understand the cost of treatment, drugs, surgery. This is what unsubsidized medical care looks like.
Our vet was amazing with our cat. She gave us all the options for treating his cancer including Chemo, but was clear it was incurable, and chemo would merely extend his life by six months at best. It wasn't about money for us, it was about his quality of life, and at 15 we weren't going to drag our boy who hated being in his basket as it was on a two hour journey to the vet who could do the chemo.
When we made the painful decision, the vet said she thought we were right, but she had to give us options because many people want that choice. They all couldn't have been kinder as after a few months palliative care at home with painkillers, we had to say our goodbyes.
Thank you for all you do.