Help stimulate NZ's economy. The prices start at $10 USD. For that you'll get a beta key and the equivalent of the money you paid in microtransaction points. Pay more than the minimum for the soundtrack, an in-game pet kiwi, more beta keys, et cetera. More info in the link.
Does the word "microtransaction" scare you? Check this out:
Path of Exile is completely free to download and play. We never intend to charge for content or access to the released game, but we are happy to offer early Beta access for those who support us during this important time. In order to fund the development and continued expansion of Path of Exile, we offer a range of ethical microtransactions that allow you to distinguish yourself in the world of Wraeclast without receiving any gameplay advantage. We are completely opposed to the concept of “pay2win”.
This is still a F2P game so you could always wait for its actual release or for the open beta (estimated date June 2012).
I was really impressed by what I played during the stress test beta access so I'm sure I'll bite. I still don't know if I'll drop the minimum or $25 for that pet kiwi and soundtrack.