So, as the "money" person involved in the Our Shirts the last 6 or 7 years, I can tell you there are razor thin margins, as the shirt really isn't designed with profit in mind. We ask students to submit a design for front and back, we add the Our Shirt logo to the sleeve (one year it was on the chest, but most years on the sleeve). One of the things I do is make sure we don't use too many colors in the print, to be able to keep the cost low. The sleeve is always a 1 color imprint, and I try to keep the front to 3 colors and the back to 2. But the dark green shirt can act as an extra color by having spaces where the shirt shows through in the design.
The bookstore sells them for no profit, they simply return the money to SG. They do this to drive business in their doors, as most people buy other stuff too.
SG does give some away. so when the price point was $5, I tried to keep the cost under $4.50. This year the cost crept over $5, so we bumped to $6, with the hope we can leave it at $6 for a while before having to bump it again. The goal is for the program to pay for itself, but profit really isn't a concern. It is meant to build school spirit on campus and be a service to students.