Every once in a while, I move VM images between machines. Even at 1Gbps, it's a drag to sit there and watch them transfer. Not really a big deal, but it'd be nice to see them move faster.
Externally:
I back up my Google Drive periodically. 500GB takes a while to transfer.
Do you download the whole thing each time, vs just changed files?
Either way, (scheduled!) periodic backups sounds like a thing that could happen over trough (well, while you're sleeping), in which case a 200Mbps connection would be more than adequate for your use case (~5.6 hours for 500GB).
The numbers obviously scale linearly with the size of your download (a common anecdote I hear re: people filling up TBs of hard drives is via lots of RAW photos), so in that scenario, you'd need to transfer 30-40TB overnight (8 hours) in order to saturate a 10G uplink; you'd likely saturate hard drive write speeds first, not to mention you'd need multiple HDDs/SSDs connected to even store that much data in the first place.