if you ask for an =5mW laser from Arnold (not >5mW or <5mW), he will calibrate it to =5mW for you.
From what I've heard of AtlasNova (Arnold, same person), you essentially get what you paid for. Buy one from his eBay store (seller id: abeland1) for $50-$60 and it will likely be closer to 5mW than if bought from his website for $79.