I’ll give you the simplest explanation I can imagine.
After labor and all costs, you turn a profit of $1 on a sale.
That’s a positive sale. You can make 10 of these a day.
How long will you be in business?
You will be in business as long as you are turning a profit. With all costs accounted for, then having an extra dollar off the sell is nice. Are you hinting that not all costs may be accounted for and surprise expenses will sink you?
If you have all of your costs accounted for, you can stay in business indefinitely and never turn a positive dime. As long as you aren’t turning negative, you can stay in. Even turning a negative margin, most businesses can be run for years if cash flow is monitored. It’s a losing game, but the money is there.