Go to your local screen printer. You'll actually be able to see what you're getting, as well as negotiate prices. Online, well, it can either go right or wrong.
my snowboard shop call revival shop 717 468 9451 they do screen printing, talk to eric kerns tellim worf sent you and they will hook you up. lots cheeper then custominc.com and the others
i know you want a site that makes them, but iv made a couple sick tee's before using stencils and fabric spray paint from a craft store. its prety cheap and looks dope
my friend's parent have a printing company so if you want you could go for like 10$ for 24 shirts printed in one color + the t shit wich are like 3 bucks each + the dye which isnt so expensive if you buy 24 shirts so like 320 for 24 shirts idk if you just wanted one then its not a great deal but if you wanted to print them for a company then its a good deal since you can sell them like 20$ each and you buy them like less than 15 each