There's a new option to get instant access to the AirMech beta on Steam, which is to buy the $10 Steam Starter Pack:
http://store.steampowered.com/app/216172/
Similar to the previous Starter Pack, this includes Gold VIP, 10 days of both Kudos and XP Boosts, and 7500 Diamonds. And instant Steam access of course.
And yes, this is technically a different Pack, so if Steam lets you buy it then you can get this in addition to the existing Starter Pack if you really want. Or buy it for a friend! :D