I think you are looking for deep insight and the point that was being made was shallow. If I make $3000 in profit, at 30% margin, I have to have $10000 in sales

I think you are looking for deep insight and the point that was being made was shallow. If I make $3000 in profit, at 30% margin, I have to have $10000 in sales. It follows that if I have an unexpected expense of $300, it will require $1000 in sales to have generate enough profit to cover the expense.