The release of Act 1 existed partly to fund the development of Act 2, so the back half of the game isn't ready to go just yet. Those who purchase ahead of Act 2's release will be given the conclusion as a free update, according to Double Fine.
Double Fine also announced a slew of statistics regarding Broken Age's production, in case you're the type who was ever curious about just how many lines of code go into creating a game like this. (Hint: it's a lot.) It's also been a time-consuming project: over the course of 22 months (or 339 man-months), the team has created 1,181 cutscenes, recorded 4,417 lines of voice, and consumed more than 680 gallons of coffee. Broken Age also takes 15 minutes (at a resolution of 1024x768) to show off 12,846 name strings during the credits.
Broken Age: it's kind of a big deal.
Update: The sale for Broken Age has come to its conclusion. The game is $24.99 once more.