Buy Dota 2 - Steam Marketplace
Instead of spending 30 USD to purchase an early access copy of Dota 2, you can now buy Dota 2 for just a few cents from the Steam Marketplace.
To purchase a copy, just go to the Steam Marketplace.
You can also sell your extra Dota 2 invites using the same platform.
Credits: Dota 2 Updates via Twitter