It will definitely depend on the ISP, but generally for repeated “AUP” violations they will suspend your service entirely.

Interestingly it’s often not technically the data usage that triggers this, its how much utilisation (generally peak utilisation) you cause and high data usage is a by product of that. Bandwidth from an ISP’s core network to their various POIs that customer connections come from is generally quite expensive, and residential broadband connections are fairly low margin. So lets say they’ve got 100Gbps to your POI that could realistically service many thousands of people, a single connection worth €/$10-15 a month occupying 10% of that is cause for concern.

If you do 800TB in a month on any residential service you’re getting fair use policy’ed before the first day is over, sadly.