It's possible that was the issue, but I estimated a 20gb storage partition. Maybe usage was to blame, I know the server was inefficient with reads and writes.

But what did you actually assign? EBS volumes are priced based on provisioned capacity (including throughput if you choose io2 volumes).

I just don't remember the details. As I said earlier, it's likely I made a mistake, but the process was not clear and I was not notified when my instance expense ballooned to something I clearly wasn't expecting. I never had these kinds of issues with Heroku, Linode or any other host.