There's also https://openobserve.ai, while not as stable as Grafana/Prometheus/Clickhouse, feels a bit easier to setup and manage. Though has a bit of ways to go, does the basics and more without issue.

Crazy crazy they spent so much on observability. Even with DataDog they could've optimized that spend. DataDog does lots of bad things with billing where by default, especially with on-demand instances you get charged significantly more than you should as they have (had?) pretty deficient counting towards instance hours and instances.

For example, rather than run the agent (which counts as an instance regardless of if it's on for a minute), you can send the logs, metrics, etc. directly to their ingestion endpoints and not have those instances counted towards their usage other than log and metric usage.

Maybe at that level they don't even get into actual by usage anymore, and they just negotiate arbitrary amounts for some absurd quota of use.