For installations of a few hundred instances or more, some of the SaaS offerings cost more than the engineering salaries it would take to maintain the OSS tools.
Shame that many of the OSS tools do not have any sort of corporate sponsorship, or if they do, that it doesn't cover all the work that goes into releasing OSS in this space.
Unfortunately, the post doesn't share things like: how much infra is needed and how much does it cost, how much time it took to set up, how much maintenance it needs, how long upgrades of the setup take, how much time future hacking of missing features will take, and so on. After that sort of stuff is truthfully taken into account I suspect most if not all savings would be lost.
Datadog will cost you $165,600 a year for 600 hosts. That is objectively equal to a very well paid engineer. So no, the statement is not untrue.
(I picked 600 because that was the approximate number of machines we had at my last job, where we used Graphite maintained by one guy, part time).
You included a LOT of redundancy in your OSS list. Multiple timeseries databases. Multiple collection daemons. Multiple dashboards. Multiple alerting systems (Who in their right mind would use Nagios AND Icinga?). You're effectively arguing about maintaining multiple monitoring stacks, some of which are quited aged.
Yikes. I'm sure there's discount pricing available but some of us have tens of thousands of hosts to monitor. The pricing you quoted doesn't scale. For me it might be cheaper to collect with OSS and graph with SaaS.
Indeed, I gave a list of all the tools, you only need to make a stack of about 4 to 8 of them to get the job done.
Let's say statsd + collectd (metrics collection) + graphite (aggregation) + carbon/whisper (graphite storage) + icinga (alerting) + grafana (graphing). That doesn't exactly come easy.
No offense but a single graphite is not a monitoring solution. It's just the tip of the iceberg. Monitoring does take a lot of engineering work and a lot of maintenance. You won't get away operating 600 hosts on the cheap, just think about how much are the hosts themselves.
Note: I am one of the maintainers of Diamond, a metrics collection tool written in python. https://github.com/python-diamond/Diamond