So, let’s say your coffee shop grosses $300,000 per year. You have two employees earning $25k each, so your net after payroll is $250,000. You report the $250,000 as personal income. But, you still have to pay things like rent, electricity, FICA on your payroll employees, etc. You may have a final personal net income of only $40k. Most people don't understand that you cannot spend the money you report as personal income; you have to invest it back into the business - it's there to cover expenses, and payroll whenever your accounts don't come in on time ( which is very often, these days) and a whole host of other things. But the government, and stupid employees act like it's sitting in your pocket. Its not.
In a previous life, when I was involved in operating some businesses, we used a multiplier of anywhere from 2.5 to 3.5 on employees' salaries to factor in the overhead costs. Insurance plans, payroll taxes, physical infrastructure, workman's comp, retirement matching contributions, all take their bite. An employee taking home $30,000 may actually cost the business somewhere around $60,000-$70,000 when all the indirects are tallied in.
Those are all good and necessary things to have in a business, but they cost money, and very few people, even employees of the business, know that they're there. I'm guessing the owner of a plumbing business would be lucky to be taking home 5%-10% of the gross proceeds as his/her salary if he/she has employees and any reasonable amount of overhead.