Butter certainly costs A LOT more than flour on a per unit (ounce or gram) basis. And, by weight, it probably accounts for a very large proportion of the weight of a recipe (maybe not the most, but it's up there). But you can easily check this yourself by costing out the recipe you gave to the guy. Just convert all quantities to weight (not volume) measures, and then figure out the cost of each per ounce or per gram. (His unit costs should be lower than your retail cost estimates since he should be purchasing wholesale, but using retail costs - if you don't have wholesale costs - will give you an upper bound.) Lastly, multiply the two together for each ingredient and add all for total costs.