If he doesn't feel exploited, he's not. If he was taking part in a class action, I'd assume he was.
As a student, ready access to food is a plus. I remember days working fresh produce for minimum wage at two separate jobs.
At one, my pay was docked when there was a power outage because we couldn't work, and I quit on the spot. The attitude of the owner/manager was demeaning and he never had anything positive to say, and his extended family ran the joint like a tribe of despots. We had arguments over standards of quality control where I was threatened with docked pay for disposing of rotten fruit. It was an oppressive, exploitative environment.
At the next, I was paid at the same rate. The section manager gave me a coffee chill after every bi-weekly unloading of new stock delivery. I was never pressured into feeling guilty that study took priority over work. I was a "token Aussie" among a workforce that was 50% indian, 20% Pakistani, 10% Iranian, 10% European and 10% Asian. They worked hard and lived 10 to a house, but everyone was friendly. It was impossible to feel exploited with respect to their work ethic, and ironically I felt like part of the family.
At both I was vaguely aware of "cash under the table" on public holidays for some family members / internationals, I'd assume as a way to get around visa limits or dodge tax. Many minimum wage workers don't care if they are paid less, but it's tax free and it's the same in the hand at the end of the day.
I'm not sure what category your mate falls into, but if he's sufficiently fed, financed and his work environment is pleasant, I doubt he feels exploited. Cash is only part of the equation.
