It depends where you are and what you feed. If you're feeding locally grown, seasonal fruit and vegetables, then it will be cheaper. If you live in a climate where, for example, tropical fruit has to be imported or grown in a greenhouse, then that will drive costs up.
For example, for me, things like carrots, peas, broccoli, spinach and butternut squash are relatively cheap and easy to obtain. If I were to add more tropical fruit like mangoes, papaya and dragonfruit, it would drive my costs up a lot because these fruits have to be imported into the UK. However, if I lived in India, I would be able to buy locally grown mangoes very cheaply when they are in season.