All the "ridiculously well paid" unionized blue collar workers I know are the people who work a ton of hours of overtime in an environment where their seniority permits them to get first dibs.
They are outnumbers ~2:1 by the blue collar workers I know who make that kind of money by working for themselves or by making themselves so indispensable to some employer that the employer pays them well above market to retain their experience in a non-union environment (e.g. the maintenance guy at a factory who's been there forever and a half and knows exactly why everything is the way it is, this maps pretty well to a lot of the highly paid "architect" positions that a lot of tech BigCos have).
I'm not sure how these situations map to a salaried workplace.
Unions control supply. It takes over 10 years to get into the longshoremans union, but once you do, you'll make $220k a year. It's because the union puts most of the work on the people trying to get into the union earning $14/hr so they can pay huge sums to the unionized worker. It's a cartel, like OPEC.