> Unfortunately, the fee ended up being so cost prohibitive that it was out of reach for us as a small startup company and we had to abandon our catalog and cloud ambitions.
Well, yes. In 2018 I created a datasource plugin for ClickHouse [1], and back then it was just a matter of creating a PR to Grafana's repo. Now, we created a plugin (also open source) for VictoriaMetrics [2], and the signing fee has become a concern. Worth to mention that, as I understand, it is an annual fee.
I totally understand that, as a marketplace owner, Grafana Labs has all the rights to decide what to do with it. But it indeed looks like a roadblock for 3rd party development.