I have to admit that this has been one of the most difficult things for me to figure out. I want to be fair in what I charge, but at the same time, I know that I need to know that my time has been worth the amount of money that I have charged.
I'm not sure what size hoop you use, or the kinds of designs that you plan to offer (density or stitch time), but I know that I can't generally embroider a design in less than an hour. Some appliques that only have a few layers may be completed in 45 minutes. You also have to count in the expense of fabric for appliques, the time it takes to perfectly hoop for proper placement, etc.
Even if you are able to hoop & stitch in an hour, that is just for the shirt. When you add the shorts, even if they're easy fits, you have the time that it takes to purchase fabrics, wash/dry them, cut out the pattern & stitch. I would think that the absolute minimum amount of time that you can count on to make an outfit is 3 hours. And that's minimum.
If your supply cost is $10, and you work 3 hours on an outfit, your paying yourself $5/hour. That's not even minimum wage. And that's calculating only 3 hours of labor.
It may be a good idea to look around etsy and see what others are charging for similar levels of work. It would be unfortunate to undersell yourself, and then end up with a lot of orders that is impossible for you to fill because you've sold them for so little.
Of course, that's just one opinion - so take it for what it's worth. I just don't want you to sell yourself short.