Neither of which is true in the real world.
The assumptions are only bad if they prevent the simple models from being useful, and the existence of a scenario where a model's simplifying assumptions prevent it from being useful does not prove that the model is worthless.
This…is not true. What theory are you referring to?
Classical economic theory predicts literally the opposite. It predicts the prices will go up exactly as if the base materials became more expensive. Classical economic theory predicts that free market produces lowest possible prices and thus any tarif means price up.
Its a long time known flaw in economics. Im sure there are better models but i still agree with GP, the scientific field of economics is still a joke on par with psychology.
It's like doing physics where you assume perfectly uniform spherical objects in a vacuum. It isn't worthless just because that isn't how the real world works, but depending on the circumstance it can also give you incorrect results, and sometimes even be way off.
In real world markets economics considers elasticity, arbitrage, and distribution of market information between producers, wholesalers, retailers, buyers etc. But very little of that finds its way into op-eds or blogs aimed at a non-academic audience.
This is incorrect. Lack of information is priced in as "risk".
... Wait, why on earth would businesses do that? "Yeah, we're in the business of buying X for a dollar and selling it for 90 cents". What economic theory are you referring to that makes that in any way plausible?
When input prices go up, output prices go up, and usually consumption falls.
Insurance companies totally operate on evaluating and quantifying risk.