Air freight China to US is very roughly $3/KG. Assume T-shirts (as a light weight good that is going to trend lower price), at an ASP of $5 and weight of 150g. A $30 order (Shein minimum for free shipping) is going to be 6 shirts at 900g for a cost of $2.70. Surepost/Smartpost tier delivery is $5 or lower; even retail-available services would be $7. In comparison, Amazon FBA for 2 shirts at $15 each would charge $7.16 for fulfillment. At December rates, they would also have charged $5.1 in platform fees, which was reduced to as low as $1.5 now due to this competition. That's $12.26 in fulfillment cost for the Amazon order of 2 T-shirts, compared to 6 T-shirts shipped China to US door for $8.70 est.
The above is generous to Amazon. 6 shirts for $5 each on Amazon would cost $22.98-26.58 to sell, and they have an array of additional fees.
It also ignores FBA freight costs - sea freight and duties/tariffs that D2C air avoids due to de minimis. On the other side, I'm ignoring fixed/semi-fixed platform costs and pick/pack costs; I have no idea what that costs in China, but it has to be a tiny fraction of the cost in the US.
> 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.