Public health insurance costs are based on your (pre-tax) income and are generally calculated at around 18% of your salary (2022). The total cost is made up of health insurance + long-term care insurance (both are mandatory and bundled together with public providers).
However, the German system assumes you'll be earning at least €1061.67 per month, so even if you earn less than that you'll still be paying the minimum of around €200 each month. And no matter how much you earn, the highest contribution you'll make tops out around €900 per month*
Income: €1000 - TK cost: around €200
Income: €1500 - TK cost: around €279
Income: €2000 - TK cost: around €372
Income: €3000 - TK cost: around €547
Income: €4000 - TK cost: around €744
Income: €5000 - TK cost: around €900
*if you have children you may pay slightly less.