Searching the web for new Agile games I came across: You sunk my Methodology. This game seemed like a strong metaphor to show the power of early feedback, while using Scrum.
Each shot costs 10.000 and when you sink a ship you get the_ships_size * 50.000 (e.g. the submarine of size 3 will reward you with 150.000). If you keep track of the balance after each iteration, you could also try to get across the idea that stopping after a few iterations might give 'good enough' rewards.
It can be downloaded from our GitHub repository as a zip or you can take a look at our code. Just double click on the index.html (in the public folder) to start a game.
**Update: Now also direct playable on GitHub.