Oh yeah, I am aware. Mostly here I would question the idea to have multi-AZ redundancy and using a manage service for DB (which indeed is expensive). All of this when a 5$ VPS could host the same (maybe still using s3 for storage) and accept the few hours downtime in the rare event your VPS explodes and you need to restore it from a backup.
So from my PoV this is absolutely overkill but I concede that it depends a lot on the requirements. I can't ever imagine having requirements so tight that need such infra to run (in fact, I think not even most businesses have these requirements, I have written on the topic at https://loudwhisper.me/blog/hating-clouds/) for my personal stuff...
Plus, at this point why not using directly managed Nextcloud (or alternatives)... If anyway you use a managed storage, runtime and database, in a vendor lock...