The Skywalker Sports modular jungle gym system is on sale a JCPenny for $408. Currently, there is also 10% CB from a popular site which brings the final price about $150 lower than amazon. They also have the monkey bar module for $125 which seems to be the lowest around.
Base (required) $408:
Monkey Bars $125:
There are 2 more modules available for this system including a suspension bridge and swingset but their prices for these 2 are nothing special. These can be configured in a lot of different ways which seems perfect for those of us with smaller back yards. Don't forget your cash back!