Yeah I dunno about this, and the grafana service. They’re not exactly complicated to run on their own. At this pricing you may as well be on Datadog.
Prometheus is a bit of a different story. It does have some operational overhead when you get to a certain point, and scaling it out is not always trivial.
Assuming it works, there is value-add on this one, and the pricing is more in line with active use (ie, a cost+ model, which is more typical of AWS services)
In my experience ES has been one of the easiest clustered / highly available and sharded systems I've ever run - especially for how incredibly performant and reliable it is.
I've generally found that beyond right sizing your nodes, indexes and shard configuration - it pretty much just works without ever really having issues.