Do you have any family or friends that are willing to let a small NAS sit around somewhere? Or host a friends backup and return they host your backup? For me, this approach works well and is probably as cheap as it can get. To just backup some data over the internet, any cheap old NAS will do. I have an old NAS sitting at my parents and just manually turn it on when I’m visiting. A small startup script runs rsync without further interaction and shuts down when finished.