Can we calculate manufacturing cost of solar system?

TRUE costs are different for CELL manufacturers than they are for PANEL and inverter manufacturers, regardless of tax incentives or after-the-fact rebates. ANY manufacturer worth their salt knows to the penny the per unit cost and every component of cost going into their product on a daily basis. Production and supply chain is where you make or break your bottom line.

Cells are mostly poly or mono silicon molded under pressure and heat and infused with mixtures of gallium, copper & other conductive materials, mostly under automated control. R&D, capex equipment and utilities are the biggest cost components. A buck per potential watt on mass-produced Si and maybe halt that on thin film would be my assumption.

Panels and inverters require much more human labor per unit, which you know if you've ever wired & soldered a parallel string array. Most manufacturers buy the cells at a markup before assembly. Storage, freight and handling eat up more $$. Assume $3.50 per watt.

Labor, freight, installation, engineering, planning and SGA should make up the rest - which is why $7.50 per watt of installed PV and $6 / therm on thermal are general cost thumbprints.
How can you calculate rebates in manufacturing cost when they vary by state and even utility? It would be completely irresponsible from an engineering and accounting side to calculate after the fact cost deferrals into the manufacturing process. As an investor, I'd want to know my true cost structure before I started approaching the market and pricing anything in a competitive environment.