If you are a fan of Sid Meier's games then you should check out the latest humble bundle. Here's a list of the games you can get for less than $20

[url]https://www.humblebundle.com[url]

$1 Tier (Each item is a separate key)
Sid Meier's Civilization III Complete
Sid Meier's Civilization IV Complete
Sid Meier's Ace Patrol
Sid Meier's Ace Patrol: Pacific Skies
Sid Meier's Railroads!

BTA Tier (Each item is a separate key)
Sid Meier's Civilization V
Sid Meier's Civilization V: Gods and Kings DLC
Sid Meier's Civilization V: Scrambled Nations Map Pack
Sid Meier's Civilization V: Scrambled Continents Map Pack
Sid Meier's Pirates!

$15 Tier
Sid Meier's Civilization V: Brave New World Expansion Pack

Basically how it works is for $1 you can get the first tier set of games. That's 5 games for $1 or whatever price you decide.
With the BTA Tier there is an average amount that people are buying the bundle for and if you beat it by even a cent you get the games listed in that tier. If you decide to buy the whole thing for $15 or more then you get everything that is listed. I bought the bundle for $15.30USD which is just under $20NZD and am currently downloading them on Steam.