While Nagios is open source and "free," it has hidden time and effort sinks that can really add up.

 

ChristineB has a blog that outlines Five Reasons Free Costs Too Much.

 

Here's a the big five:

  • Time consuming
  • Poor scalability
  • Diffuculty adding apps
  • DIY attitude
  • High switching costs

 

Read more about these money sinks here.