How can a 2 person plumbing company possibly clear $250,000 a year?

If Joe the Plumber has an operation that makes $250,000.00 a year in taxable profit, why did I go to medical school? Seems like if after expenses, payrolls, taxes, supplies, vehicles, advertising, rent, utilities, licenses, and all the other deductibles that a small business can claim, that if there is $250K left over, they should pay some taxes. This is not socialism, it is taxation and that runs the country.