We've just added support for the new region in our Aiven DBaaS platform. You can launch managed Kafka, Cassandra, PostgreSQL & other clusters in AWS Stockholm at https://aiven.io/
Our services utilize T3, M5, R5 and I3 instance types, so we offer e.g. 4GB RAM PostgreSQL service which isn't available in RDS, but right now we don't have instances smaller than that in AWS.
I can see various instance prices (EC2, RDS, Elasticsearch) being 5% cheaper in Stockholm than in Ireland.
However, eu-north-1 has very limited instance types available when compared to eu-west-1, which could make you pay up to 10x more in Stockholm if you have been comfortable using t2 RDS instances in Ireland for your (test or even production) environments.
It makes no sense for AWS to launch old instance generations in a new region. Also what do you mean by 10x more if you were using t2? t3 is available in Stockholm and cheaper than t2 (and t3 in Ireland).
If you were running your databases on T2 instances on regions supporting it, migrating to the cheapest available RDS instance type in eu-north-1 would cost $0.374/hr on-demand. That's over 9 times more than the price of db.t2.micro in eu-west-1.
Our services utilize T3, M5, R5 and I3 instance types, so we offer e.g. 4GB RAM PostgreSQL service which isn't available in RDS, but right now we don't have instances smaller than that in AWS.