Depends on your usage, how much you value silence, cooling, looks, space, features, etc.
Personally, I could see myself paying upto 400 dollars if thats how much it offered. A case is not something you need to buy every new build, so I do not see such a big problem with buying a nice one.
Also, I don't like my cases looking like cheap pieces of crap, or toys, and I don't like it when my cases are loud. That's why I would never want to settle with something cheap like the Antec 900.
The NZXT Zero also looks like a gimmicky case. 5 120mm intakes paired with 2 120mm exhausts and 1 80mm exhaust = undesirable, at least with the stock fans, I'm assuming. It can be changed around to be a bit more desirable, of course.. but I'd still rather buy other cases.. =\