Gluten-free foods are expensive. It takes research and development to produce gluten-free products and raw ingredients for the products must be sourced from reliable, certified suppliers. These costs are passed on to the consumer.
Remember that natural foods - vegetables, plain meat and fish, potatoes, rice, fruit etc. are all gluten-free at no extra cost. There are several ways to get some money back on these expenses.
In addition there's also some information on health insurance for coeliacs.