Your profit is determined by many factors, including the product itself. A high end shirt has a higher base cost than a basic tee. Another big factor is the number of print locations. We HIGHLY recommend that you only design the front of your tee. Adding a second location, like a back imprint, roughly doubles the printing cost.
You will also want to keep your design colors low. One color is the least expensive to print. Lastly, your profit will be determined by your selling price and quantity sold. We use a tiered pricing matrix, so the more you sell, the cheaper it is for us to print. That in-turn increases your margin per item sold. So simply put, the more you sell, the more you raise.