Hi all,
Our company does commercial HVACR installs and I'm trying to improve our ducting department. Our metalcraft manager is a very competent guy who is very practical and hands on but has little understanding of pricing and how to conduct accurate and consistent costing sheets in a timely manner (the large amount of work we win is through reputation and repeat business). Because of this I'm trying to build a excel model for him so that he can do his take offs from drawings and plug them into a model which spits out the price for various duct sizes, transitions etc. etc. I've figured out most of it but am struggling to figure out how to model economies for scale for shop hours for the construction of ducts, and also efficient uses of sheet metal which also accounts for the waste pieces in the price. We use standard sheets which are 1200mm x 2400mm

For example if we're building a 200 x 200 duct 2.4m long it might take 2 man hours, if we're building an 800 x 400 duct 2.4m long it might take 4 man hours, and if we're building a 2000mm x 1200mm duct 2.4m long it might take 10 man hours but the relationship is not linear between any of the variables. It's the same principle as economies of scale.

I was hoping someone might have some insight on how to model this or curious if anyone has done something like this before?
I've built something similar for cool rooms and freezer rooms and it makes things much faster and easier as all we need to do is worry about the refrigeration equipment side of things as the panels, extrusions, doors etc. are fixed prices which scale based on the room dimensions.