I think this($5/box) model is preferable to the one currently offered. It strikes me that you are selling a $30 company t-shirt and that sounds expensive. Any printing company is able to duplicate your model very easily, undercut your pricing, and probably do it more efficiently with existing resources (admittedly, I don't know your resources, you may have great production and shipping capabilities already built out).

I have worked remote for a few different companies, and the more compelling offer is a service with a high-degree of customization, which can include a t-shirt and some stickers, too. Plus, you could charge more for curating and purchasing. Suppliers may also pay you to be part of your curated offering.