Oh wow, one of the biggest reasons we picked Google Cloud was that you did not have to pay a flat fee for their managed Kubernetes service. Luckily there is Kubernetes support across all Cloud Providers so we're happy we're not vendor locked in. (biggest reason we picked Kubernetes in the first place.)
We were thinking of using Stackdriver for logging, but we were scared of vendor locked in due to price increases or other changes that we've been warned about with Google. In this case, I think it's safe to say we'll be using Prometheus + Grafana + Loki instead since there may be a random Stackdriver flat fee introduced or some other weird fee and we may need to migrate out of Google.
Stackdriver is terrible, and super expensive for what it is. We ran a dedicated Fluentd in GKE for a long time to work around its shortcomings (GKE also uses/used Fluentd to shuffle logs into Stackdriver), then switched to using Loki + Promtail + Grafana, which has been excellent.
The last place I worked, with a couple of petabytes of monthly Stackdriver logs and a full embrace of almost every GKE/GCP tool, also switched to Prometheus + Grafana due to a lack of functionality within Stackdriver. I think you're making a good choice.
We were thinking of using Stackdriver for logging, but we were scared of vendor locked in due to price increases or other changes that we've been warned about with Google. In this case, I think it's safe to say we'll be using Prometheus + Grafana + Loki instead since there may be a random Stackdriver flat fee introduced or some other weird fee and we may need to migrate out of Google.