This was the reason that we ended up choosing Datadog over Grafana Cloud at my previous place. Most metrics came from "integrations", and Datadog doesn't charge extra for any of those (they just curate them so that the cardinality can't get too high), whereas Grafana charges (charged?) for each metric and didn't provide anything to reduce cardinality. Their solution was to suggest we did more engineering and ran more infrastructure to aggregate before sending to them, not something we wanted to invest in given that the whole point was to not self-host Grafana anymore.

Datadog is expensive, but at least we were only making these decisions for the ~hundreds of custom business metrics, and not the ~tens of thousands of metrics from our infrastructure.