This is a commonly made false comparison: employed physician vs. self-employed plumber. You've combined two jobs (plumber + small business manager), then assume

This is a commonly made false comparison: employed physician vs. self-employed plumber. You've combined two jobs (plumber + small business manager), then assumed that the plumber is better than competent at both. This will not compare favorably at the margin if you compare e.g. to a surgeon who opens a plastic surgery practice, or uses his surgical skill to found Intuitive Surgical. Either compare averages or admit that there's no point comparing when you already know the outcome you want.