Funny, aren't you USers used to not knowing what you'll pay for something because the advertised prices don't include sales taxes and administrative fees and whatever fees and service charges and tips that are not service charges?
Prices changing after a preorder is completely different and not anything US specific.
I think it may even be illegal for consumer prices. What they display or list in the contract is what you pay.
But on the other hand I'm used to paying import taxes separately when ordering something from outside the EU.
But that doesn't have much to do with a price increasing weeks or months after paying for a preorder.
Tax policies change from the Truth Social post to the press conference.
FWIW, I'm in south-Europe, maybe that's why I got surprised I wouldn't have known the final price until the device would land in my hand?
Large stores can afford to precalculate this and use a service that will handle taxes for you, small stores not so much so you may end paying it personally on receiving the package. But they can afford to precalculate it if the taxes are known in advance (usually starts at whatever your country's VAT rate is).
Now in this case, shipping to the US looks like it will be randomly taxed depending on the phase of the moon and how well Trump has slept last night, so this warning is fair. You can't expect them to absorb a 50% import tax if it's established tomorrow.
Sure, and as you also seem familiar with, you know it's pretty trivial to calculate yourself when you place your order :)
So far, I've never bought something internationally, then before shipping the tax laws changed enough that the toll and/or tax payment was different than I expected.