FYI, the Aiven database service allows you to run multiple database per instance. HA plans for Aiven start at US$200/mo and are available in multiple clouds including AWS and Google, see https://aiven.io/postgresql#comparison
Aiven services are available on UpCloud and we're friends with the UpCloud people as we're both based in Helsinki and have met at various events, but there's no other connection between the companies.