I understand that your question asks how he relates to union supers; nevertheless, I wanted to make a few points and answer your question...

Many of my supers are either forgoing a raise this year, or receiving some benefits in lieu of a raise.

The purpose of a live in super is that they have the understanding that they are on call 24/7 and should be available for all emergencies and hour shifts (in case of snow, etc..)Unless he punches a clock, and is mandated to remain out of his apartment during those hours, I am certain he makes these hours up on his own.

A super earning 50K, plus rent, phone, electric, gas and ?? paid equates to 75-90K per year, depending on the apartment size and market value...and more if there are health and/or retirement and other benefits added.

All that said... A union super on the job for that long can make more or less depending on the benefit package, etc... but you are in line with where it should be (this is also dependant upon the building size and finances).

I suppose my point is, why are you comparing him to a union super? the whole point of being non-union is just that!
You can provide many deductable benefits that are mutually beneficial to both the super and the buildings budget and bottom line.... these ideas may be a good topic for a separate post?

Best
~AR