http://swz.salary.com/salarywizard/layouthtmls/swzl_compresult_national_SC16000004.html
The median expected salary for a typical Plumber I in the United States is $37,514.
You can see how, if Joe owns a small plumbing business making $255k per year and he hires two or three plumbers, a tax increase can kill his business or get one of his plumbers fired.
Called my typical Plumber Husband and he said that's about what he makes a year.