Well actually one meaning of the English word tariff is the same as the German meaning, although it's not as widely used. To quote Wiktionary:
> tariff (plural tariffs)
1. A system of government-imposed duties levied on imported or exported goods; a list of such duties, or the duties themselves.
2. A schedule of rates, fees or prices.
3. (British) A sentence determined according to a scale of standard penalties for certain categories of crime.
...so Hetzner's usage of the word is technically correct™, even though native speakers might not use it in this context.
It's closer to industry jargon at this point in American English. Search for LTL tariffs, for example, and you'll find a very long list of trucking companies publishing their fees and terms as tariffs.
It's completely normal usage in Britain.
"I changed electricity provider to one with an EV tariff."