Pre-orders of all editions grant "early" access to the open multiplayer beta. The Vault Edition grants access to a "Red Team 141" operator pack, a "FJX Cinder Weapon Vault" pack, plus access to the Battle Pass of a Season for Modern Warfare II (dependent on the time of purchase), and double XP tokens.
'Modern Warfare 2' is jumping on the price hike bandwagon and players aren't happy about it. Unfortunately, the simple answer as to why MW2 is set at such a high price is that $70 has become the new standard for triple-A games.