No single percentage proves that a price works
A price can show a positive unit margin and still fail to cover fixed costs, cash timing, returns, capacity, owner compensation, financing, or taxes. Carry the same source records and time basis through the sequence above, then compare more than one realistic sales-volume and cost scenario.
Use realized prices after expected discounts, model commissions and payment fees where they actually change with sales, and keep separately collected transaction tax outside the operating comparison unless the applicable accounting or tax rule requires different treatment.
These tools provide simplified educational arithmetic, not accounting, tax, legal, payroll, financial, or pricing advice. Verify contracts, cost records, capacity, current tax rules, invoice treatment, and reporting requirements with appropriate official sources and qualified professionals.