I'm finding the process of building spreadsheets for things I bake interesting, especially the costing data.
Recently I've set up a spreadsheet for pie dough and one for apple pie filling.
A double crust costs between $1.25 and $1.75 depending on the size of the pie pan and the thickness of the pie crust. (These days I'm trending towards thinner crusts.) Butter is, not surprisingly, the most expensive ingredient.
Apple pie filling for a 9 1/2 inch pie pan (not quite deep dish but close) runs about $3.80, the biggest variable and expense is the cost of the apples.