Batteries do not count in your withholding allowance via update 15.
Make your prices based on equivalent materials, For instance if you cut up an old flag pole to use the tubing, don't price out a flag pole (unless you used it for one) price out aluminum tube that is the same or very close size. As you could have made it from that tube if you had it, but you already had that flag pole. This will save you some budget allowance on some parts.
www.mcmaster.com <Mcmaster Carr industrial supply
They will probably have a price for just about everything you used use pricing from your local home center for wood items, etc. This is very general and would work in most cases, however find an item that is as close as you can get to the actual part for your pricing.