Assuming it applies to sale shirts too, you could get these two shirts from as low as $11 plus shipping. Check out the sale shirts here.
Example shirts:

A shop I don’t think I’d ever heard of before. Its having a 25% off sale for the next 15 days. There doesnt appear to be all that much stock left (only two girls tees for example) but they do have this super awesome monkey badge for €0.90 (yes i am easily pleased)

T-shirt wise you [...]

Here is last week’s recap:
Monday, June 18, 2007$10 Tees at Ten Bills View Post
Wednesday, June 20, 2007New Competition – $100 Threadless voucher + Mega Swagbag View Post
Friday, June 22, 200715% off Coupon for Bigbadbuffalo (Coupon: welikeu) View Post

Three new shirts from one of the most popular sites on the net.
There are also about 25 shirts on Sale here

Plenty of other shirts ranging from $5.99 to $13.99

Excuse me while I just indulge myself a little bit on here. I haven’t posted much lately, I’ve been busy at SS and giving some of my other blogs some more time, and getting the ball rolling on some long planned projects.
Anyway I was looking at my stats just a minute ago and I realised [...]