I second that it could be an allergy. Not sure how to test for that, though.
I know how you feel about the money thing. My mom always complains when I get my bun's teeth trimmed every second month, which costs about $80. But I'm the one paying for it, so I don't get what her problem is. Same with my cat. I have to pay for his vet bills too, and my parents both complain about how high they tend to get. Even the vet wasn't very supportive. She bluntly asked me once when my cat was diagnosed with diabetes "How much are you going to spend on an old cat?"!!! Needless to say, I was very offended. She's a vet yet! Of all people, she should understand the value of animal life.