I see this claim a lot in different contexts, and personally have never quite understood who it really talks about.
It cannot talk about everyone, because there are many different kinds of people and work sectors. I'd expect the motivational priorities to exist on a continuum, on which some people are more motivated by money than others. Also, the "adequate compensation" varies from person to person; some are happy with some level, some are never happy.
I mean, I find it extremely hard to believe that things like, say, "respect from co-workers" and "interesting work tasks" would factor in as the primary source of motivation for e.g. anyone working a low-paying job and living from paycheck to paycheck, regardless of who exactly (worker, employer, state, someone else) thinks the compensation is adequate. In contrast, for someone who already possesses a hefty surplus of money, obtaining more money probably plays a smaller role in the overall motivation.
However, none of this means that it's generalizeable to say all working people are not primarily motivated by money (or are primarily motivated, for that matter). One could just as well argue the opposite: (for some people) money turns out to be really high on the list of things which motivates them. Whichever way, it still is weird to claim this as an absolute, applying to everyone.
To put this into a more concrete context: a C-suite executive of a Fortune 500 company might say "money is not my primary motivation, energizing coffee machine discussions, personal fulfillment, yada yada" -- they already are on a level with plenty of material wealth and opportunities for recreation. In contrast, a single parent sanitary worker is unlikely to claim motivation comes from "I'm energized by the interesting work tasks" or something else than money; certainly they are motivated by being able to pay rent and buy food for their children and would rather have more money than less.