Speaking as a former screen printer, the material costs are very low, except for very elaborate prints: clear or glitter inks, adhesive and foil, partially embroidered shirts, water-based inks with or without burning out the underlying dye in the shirt itself, and certain gradient effects like the Zune logo that required a very steady hand and some experience to produce. The last was my favorite; the complex prints were mostly to the demands of Vegas casinos.
With the caveat that my career was interesting but fairly brief, I believe that I may offer a cost analysis of what exactly the profit potential is here. The shirts and inks themselves cost a pittance, less than five dollars each as a rule. Production equipment can be moderately expensive and requires a moderate amount of warehouse space, but the highest operating cost is almost certainly going to be the Art department. Complex prints take lots of expensive man-hours and back-and-forth with clients to produce, and even simple ones need someone with a bit of domain knowledge to produce. Most designs will be spot colors rather than CMYK, because CMYK tends to look like your grandma's Christmas sweatshirt rather than e.g. a photo.
So, if you can outsource half your art department, and avoid complex designs, and avoid the need for a lot of expensive machinery, you're pretty much where these guys are at. Your big competition is likely to be Chinese, and so the real mass market (Target, Wal Mart, etc) is more or less out of reach, so if you can focus more on smaller runs of boutique prints then you can join the handful of other companies competing in this space, and make -- as other poster suggested -- a decent profit, an enjoyable product, and a career, but not likely a staggering amount of wealth.
Depends what you mean by real money, of course. There might not be super-startup-huge-exit money, but there's definitely make-a-small-business-you-enjoy money. And, more broadly, there's always money if you're willing to cut corners or be unethical. We're more interested in building something sustainable and something that makes people happy. T-shirts make people happy, and Cotton Bureau helps people make t-shirts which makes those people happy too.
With the caveat that my career was interesting but fairly brief, I believe that I may offer a cost analysis of what exactly the profit potential is here. The shirts and inks themselves cost a pittance, less than five dollars each as a rule. Production equipment can be moderately expensive and requires a moderate amount of warehouse space, but the highest operating cost is almost certainly going to be the Art department. Complex prints take lots of expensive man-hours and back-and-forth with clients to produce, and even simple ones need someone with a bit of domain knowledge to produce. Most designs will be spot colors rather than CMYK, because CMYK tends to look like your grandma's Christmas sweatshirt rather than e.g. a photo.
So, if you can outsource half your art department, and avoid complex designs, and avoid the need for a lot of expensive machinery, you're pretty much where these guys are at. Your big competition is likely to be Chinese, and so the real mass market (Target, Wal Mart, etc) is more or less out of reach, so if you can focus more on smaller runs of boutique prints then you can join the handful of other companies competing in this space, and make -- as other poster suggested -- a decent profit, an enjoyable product, and a career, but not likely a staggering amount of wealth.