Cheapest way to play it is to buy OA and use ARMA II Free (it requires the chenarus map from ARMA II/ ARMA II FREE) doing it this way requires a bit of iddling to install it if you google "dayz arma free" there are some easy guides (you have to move some folders is all).
Another people dont realise is if you want high resolution player models you also need the Private Military Company addon as player models are from this.