Well, I've had ArmA 2 since 2009 and I've had OA since release day. I'd say it is worth 100$, but that is because I love the game, a lot. I've been playing zombie mods since the Undead mod was released and I played Quarantine in the ArmA 1 days. If you are getting it for only DayZ, then I would say it is worth 30$, yes. If you plan on branching out to the other aspects of ArmA play, then I think you are getting the game for a bargain price.