Well, that depends on what you consider cheap. Hiring someone to manage a time series system like graphite or prometheus is going to cost you a whole lot more than $26k a year
You're ignoring half of my example scenario. $26k writing the data, $525k for querying it just for alerting, plus whatever it costs to store and to query ad-hoc. That's over half a million dollars. Even if you hire someone for $250k, you can self-host your time series system for cheaper than that.
Self-hosting isn't the only option though. For example, that hypothetical 1000 server scenario would cost $180k a year at list pricing on Datadog or SignalFX.
