Just received an email from Google Cloud -

"On June 6, 2020, your Google Kubernetes Engine (GKE) clusters will start accruing a management fee, with an exemption for all Anthos GKE clusters and one free zonal cluster.

Starting June 6, 2020, your GKE clusters will accrue a management fee of $0.10 per cluster per hour, irrespective of cluster size and topology.

We’re making some changes to the way we offer Google Kubernetes Engine (GKE). Starting June 6, 2020, your GKE clusters will accrue a management fee of $0.10 per cluster per hour, irrespective of cluster size and topology. We’re also introducing a Service Level Agreement (SLA) that’s financially backed with a guaranteed availability of 99.95% for regional clusters and 99.5% for zonal clusters running a version of GKE available through the Stable release channel. Below, you’ll find additional details about the new SLA and information to help you reduce your costs."