Awesome project!

What about hosting the data in an S3 bucket with "Requestor Pays"? You'd only have the storage cost.

Disables anonymous access (so would a Dropbox share) but reduces your cost massively.

https://docs.aws.amazon.com/AmazonS3/latest/userguide/Reques...

You wouldn't necessarily need an SQL frontend as it's readonly anyway, and there are multiple ways of letting SQLite access databases in S3 buckets, e.g. https://github.com/michalc/sqlite-s3-query