Remember the proverbial expression 'not seeing the wood for the trees'? You need to see the 'wood' first, then delve in and start examining the individual 'trees', meaning the individual items which you will be breaking down later. So a great point is to make sure that you have that overarching vision _ and if you cannot find one, then maybe it is an indication that you are obsessing on a few technical aspects that do not necessarily make up a whole business as you had imagined it. A business that makes sense and is going to be sustainable in the future is one that has that clear vision within which all the smaller parts contribute to make it successful.
Average Selling Price _ Now when you calculate your average selling price which is your cost of sales (material + labor) divided by Ƒ_gross profit), you can determine how many customers you would need and then come up with what you think your conversion rate would be for converting leads to customers, you can determine how many leads you would need. Then from this and with the aid of the U.S. Census Bureau and some basic research on your own you can actually have a pretty decent idea of what size your market is and is going to be in the future so you can see if it will support your business plan or not.