It's dirty. That is a ridiculous price for a dirty hat.
Not for the greatest hat in existence (opinion of course, but it's pretty much true). It makes sense that if the clean version costs more, the dirty version should too. Take a look at
http://backpack.tf/pricelist. It lists the price as 1.33. And with lime paint for only an added rec, that's a great deal
Edit: Also if you think I'm trying to rip you off or something, I paid almost twice the amount to get it then I'm selling it for