Anne R. Lee, a nutritionist who specializes in celiac disease, published a research paper in the Journal of Human Nutrition and Dietetics in 2007 on the topic of the price of gluten-free foods. To sum up her research in just a few words: the gluten-free diet is pricey. On average, specialty gluten-free foods (bread, pasta, cereal, waffles, cookies, crackers, pretzels, pizza, cake) cost two to three times that of their conventional counterparts. While Lee found that across the board every gluten-free product costs more than wheat-based ones, the most expensive gluten-free product costs more than wheat-based ones, the most expensive gluten-free items she surveyed were "snack" foods: crackers, cake, pretzels and the like.
Interestingly, Lee examined the cost of gluten-free foods in five different geographical regions (New York City and its metro area; Portland, Oregon; Atlanta, Georgia; Rapid City, South Dakota; and Chicago, Illinois) and in four different types of stores (regular grocers; upscale grocers; health food stores; and internet stores). Lee found that in general, geographic location didn't affect the cost of gluten-free foods as much as type of stores. Online shopping was the most expensive, though it offered the best selection, while regular grocery stores were, not surprisingly, the cheapest (and the most limited in selection).
Notably, gluten-free cereal was one food item Lee surveyed that was relatively close in cost to conventional cereal. But instead of being a bright spot for gluten-free shoppers, it probably points more to the fact that cereal in general is an expensive purchase.
It remains to be seen if the projected growth in the gluten-free marketplace meaningfully affects prices. According to Lee's research, the cost of gluten-free foods would have to come way down to match their wheat-based counterparts. And Lee cautions that for some, the prohibitive cost of gluten-free foods could be a barrier to dietary compliance.
Lee, AR et al. (2007) Economic burden of a gluten-free diet. J Hum Nutr Diet 20 pp 423-430.