I'm not so sure to be honest. It is very expensive. But being able to quickly get all of the features is fantastic for a small company. As you start to use more volume (and your bill starts growing) then it makes sense to start considering self-hosting. But for many teams with relatively small data volumes self-hosting is likely not worth the engineering time.

Out of curiosity, is there anything self-hosted that compares to data-dog RUM?

Likewise for New Relic. Unfortunately OTel and everything similar doesn't remotely come close to the usability and ease of configuration that New Relic does. Not yet, anyway...

Ideally you just implement OTel into your apps and later plug that into any metric/log/trace collector you want, so you have DataDog and Newrelic and other frontends competing based on their feature suite and price.

As it stands, this was/is trying to use DataDog's existing APM libraries to turn them into OTel for ingest into other providers.

you may want to have a look at SigNoz - https://github.com/SigNoz/signoz

PS: I am one of the maintainers

Plus they have (or had, just going off of my personal experience) very unethical sales practices.