If there's anything close to a "Super Bowl" equivalent in the world of eSports, it's The International tournament, hosted by Valve. The prize pool contains $1.6 million, but apparently that's just a starting point. By purchasing an "Interactive Compendium" for $9.99 from the Dota 2 store, you are actually contributing the the prize pool and increasing its worth.
In addition, you'll get a fancy courier which can evolve by watching matches and even make predictions and win prizes. There are even stretch goals; if enough people buy Interactive Compendiums, owners can get Battle Bonuses, new courier stages, and even an Immortal-tier item. So get to buyin'!
Speaking of The International, apparently tickets went on sale today via the Dota 2 store and sold out really quickly. Tickets were not limited, so many people ended up buying many tickets at once and are now selling them for over $200 on the Community Market, while others continuously got errors while trying to purchase a ticket. Confirming once again that people are, indeed, gigantic assholes.
So please, don't buy an International Ticket from the Community Market. Don't give in!