What's the effective tax burden on a self-employed single person making $300k in, say, Massachusetts (5% income tax; not exactly the highest in the US)?

Based on 2020 US tax brackets, standard deduction, including the both sides of FICA (capped at the social security cap for the social security part) and the medicare extra tax they are paying, I am ending up at ~37-38% effective (not marginal; marginal is 43.8%) tax or so. This individual would in my mind be excused for claiming that they pay "40% in income taxes" and is not making "millions" (though obviously is not suffering financially).