Just pointing out that what you're paying for is actually 3x these resources. By default you get a primary server and two replicas with whatever specification you choose. This is primarily for data durability, but you can also send queries to your replicas.
For sure, I personally use pgvector myself but I also don't have millions and millions of rows. I haven't messed with anything other than Pinecone so I can't speak to those services, but there's a big difference than a vector db for your own personal use and a chat app/search on a db with millions of users convos and docs, not sure how well these managed vector DB platforms scale, but you probably need the db guy anyways when you're using vectors at scale. Atleast I would.
Actual SPANN or janky "inspired by SPANN" IVF with HNSW in front? Only real SPANN (with SPTAG, and partitioning designed to work with SPTAG) delivers good results. A superficial read of the paper LOOKS like you can achieve similar results by throwing off the shelf components at it, but it doesn't actually work well.
I'm sure it works great, but at that price point, I'm stuck with self-hosting Postgres+pgvector.