The offering from Hetzner I find especially appealing are the consumer grade hardware ones. No I wouldn't host business critical services on one, but I don't have those so easy win for me price wise.
Plus Xeon’s ofc
If I was looking to scale up an existing operation considerably and minimize costs as much as possible, I'd consider spinning up e.g. a Postgres cluster or minio on their infra, which would be significantly cheaper than RDS or S3. But it's not something that I would gladly do---the storage deals provided by hyperscalers are quite reasonable, as you say.