Here is a good example. Look at our cagepress site here http://www.cafepress.com/gcmaine.
You will see the prices on some shirts I set up a long time ago. If you notice the prices you will see you are not going to get a shirt for under $14.
The prices on this page are my prices at cost(no profit).
Now think about it. If we want to make a profit off cafepress then we would have to jack the prices up to about $5 each. That would make the shirts $20 and that does not even include shipping. Shipping is $5, so now that that brings the price of the shirt up to $25.
Even without jacking up the price to make a profit the price of the shirt with shipping in almost $20. That is to much in my opinion to pay for a cotton shirt.
I can get cotton shirts like the ones above made up for $5 to $6 depending on how many I order. I usually have to at least 24 in the order but sometime I can swing a deal and get the same price on smaller order.