In short: The break-even point is the number of sales at which income equals costs — neither profit nor loss; you find it by dividing the monthly indirect costs by the margin on one sale.
Simply put: First see how much is left from one sale after direct costs (price − direct costs). Then see what a month "with the door open" costs (the indirect costs). Divide the second by the first — that is the minimum number of sales from which profit begins. Formula: indirect costs ÷ (price − direct costs per item).
Example: A coffee at €2.00 with direct costs of €0.80 leaves €1.20. Indirect costs are €1,800 a month. 1,800 ÷ 1.20 = 1,500 coffees a month — 50 a day over 30 days. At a price of €2.20: 1,800 ÷ 1.40 ≈ 1,286 (≈43 a day).
Watch out: the point moves with three levers only — the price, the direct costs per item and the indirect costs. Don't take a loan before you know it.
Source: OpenStax, "Principles of Managerial Accounting", 3.2 "Calculate a Break-Even Point in Units and Dollars" — https://openstax.org/books/principles-managerial-accounting/pages/3-2-calculate-a-break-even-point-in-units-and-dollars