Not a bad deal for premium tees which are a better quality than the regular ones. At least from my experience they last a lot longer. Regular tees really suck now, so I don't bother looking at that.
Shipping is USD$9.90 for every two pieces of the premium tees from what I can see, so take that into account.
If going for the premium tees, this is a better deal than the free shipping offers they have now and then.
I was kind of glad when Threadless dropped the quality of their tees because it made me stop buying them. I was spending way too much money and building up an unnecessarily large collection of tees. I could go months without having to do the washing… now you're saying they've added different quality options and I'm tempted again. Already have 10 tees in the cart that I have to cull back. Ugh…. not this again.