Budgeting off Revenue hides materials, subcontractor and direct costs and lets Operating Expenses bloat. Use Spendable Revenue (Revenue − Mat/Subcon/Direct) and cap Operating Expenses as a % of that.
Spendable Revenue & Operating Expenses cap
Spendable Revenue = Sales − Materials/Subcon/Direct Costs. Set your Operating Expenses cap as a % of Spendable Revenue, not Revenue.
Optional: 14-Day Payback check for new spend
Payback days = spend ÷ (profit/sale × orders/day). Must be ≤ 14 for safe testing.