RDS Serverless v2, Postgresql 15.4 high idle cpu

I set up a database to evaluate RDS Serverless v2. However it looks like that the base cost is way too high to say it would be serverless service. Database is set up to 0.5 to 2 ACU's and it is constantly loaded at ~50% writer and reader CPU. While no traffic or connections. Simple projection shows that this would mean that by the end of month it costs ~250 € to just idle this database.

So the question is that is this the normal behaviour and cost for this "serverless" cluster?