There's two things happening here. There's a tariff on Chinese goods that has to be paid by the exporter (that's new and is meant to be a punishment to China), but there are also customs duties that are levied on imported goods.
Previously, anything under $800 used to come into the US for free, but they are now being taxed and the courier needs to pay that, so they pass it onto the consumer. That's what Kit needs to pay to 4PX, so he has to charge that to the consumer.
I noticed he's starting to update his preorder listings to account for the possibility of an upcharge:
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