Very hard to say because each job, wage, and “availability” to work will be different. Some campus jobs will “run out of work” so you might not get some hours. My niece has a campus job and works for a franchise in the “Commons” dining hall. During holiday breaks, the whole Commons building is closed and she doesn’t get any hours. I worked in the graduate school office and part of my job was to collect mail (US post office, as well as, student/prof mail). Sometimes, there was no mail, especially during midterms, holidays.
Remember that these campus jobs are generally used as low incidence expenses-daily living. I would say that earning $5K per year (spread out over 10 months ) would have been the maximum if our daughter had worked all of those 20 hours over the year. I think she earned about $900 per quarter. We supplemented SOME expenses for her (like expensive fuel and maintenance costs), so she used her $900 to buy daily living supplies. So she probably made about $2700 for the year, at her campus.
She came home for some summers and worked, full time, at the amusement parks, on the weekends, and at the Vet’s office during the week. That’s where she made her savings for her college contribution.
I guess i would say that there was just too much going on, within the campus, with her studies, office hours, tutoring, and maintaining a high GPA for med school, that she did not place a high priority on working. She wanted exceptional grades.