What Gaypl said is true. Not every inch is the same, and not the cost of every thread, or machine, or any of the other variables. Figure out your cost for an hour of labor, and materials. Then, figure your skill level, the going rate in your area, any other considerations of your local area. New York City won't be the same as some backwater shop in the jungle. Only you know what an hour of your time, in your area, with your machines,etc. are worth.
Sorry, your post just made it in before mine! I can see that it is totally different where you are. In that case, you would be a better judge of that than I. All I can say, is aim high, you can always come down, but never up!