And where, exactly, is the breakdown that shows they are simply comparing barristas to crab-fishermen?

I ask because when I have looked closely at these kinds of statistics, (like those compiled for the census) the breakdown tends to be quite specific. Far from merely comparing barristas to crabbers, they compare the salaries of people working the same jobs within the same industries, and yes, in many the disparities remain. The fact that toting it all up results in an overall income disparity does not mean they are equating crab fishermen with people working the counter at Starbucks. It does mean that income disparities within various fields are consistently lopsided enough to affect the stat when they're all compiled as a group.