These estimates always ignore two things:
1) Apple already makes huge profit margins, literally the best in the industry.
2) They are greedy, they are already charging as much as they think they can get away with. If they could charge $2400, they already would be.
Basically their estimate is "to maintain their margins, this is what they would have to charge." But why assume they will just maintain their margins, *that's why the stock is down 15%*. No one who actually has skin in the game is assuming that.
Don't get me wrong, prices will go up, but I would bet virtually anything even if the full 54% is ever applied, prices won't increase nearly that much. Apple's margins will absorb a great deal of it. Don't panic on Apple's behalf.
What I find hilarious, it's the same poor reasoning the other side uses about minimum wage. No, just doubling the wage of the cashier doesn't double the price of a Big Mac. And no, just adding a 50% tariff doesn't increase the price of an iPhone 50%. Both are a stupid oversimplification.