Being in the veterinary field - I can tell you that most vets are truly not out for your money. I'm an emergency tech - so I get to be the bad person and tell people that their dog needs a $4000 bloat surgery, or a $3000 exploratory. But guess what? We have overhead. We have employees. We have bills. We cannot work for free. So yeah - there are fees. And as I said before - nothing is cut and dry. This is a 13 year old (geriatric) intact (still has balls) dog. DO you know the differentials on that?! It's insane!
And as far as the food - I cannot speak for each vet, but I can speak for the need & uses of the prescription diets. Those diets can save lives & boatloads of cash - such as the C/D or SO diet that can dissolve a dog/cats bladder crystals and stones. Or Y/D that can regulate a cats thyroid hormone so that you don't have to do very costly reactive iodine treatments.