Here is the link to the store, too much traffic at the minute though:
https://store.bistudio.com/dayz
http://store.steampowered.com/app/221100/ £19.99
What the developers say:
“DayZ Early Access is your chance to experience DayZ as it evolves throughout its development process. Be aware that our Early Access offer is a representation of our core pillars, and the framework we have created around them. It is a work in progress and therefore contains a variety of bugs. We strongly advise you not to buy and play the game at this stage unless you clearly understand what Early Access means and are interested in participating in the ongoing development cycle.”
Do bare in mind, this is an Alpha and alot of work needs to be done to it.
It is being sold similiar to the Minecraft model too, It'll become more expensive as time passes.