Price is set at the margin. If America is physically incapable of supplying 100% of its own lumber needs, then that Canadian lumber is the marginal good, and the price of 100% of lumber will go up, not just the Canadian stuff.

Two things that will prevent that:

- inertia

- it's likely that Canadian lumber before the tariffs wasn't the marginal good, wasn't the highest cost supplier. If Canadian suppliers were making 10% more profit than the previously marginal supplier, the price will go up 40% instead of 50%, Canadian suppliers absorbing that 10%.

Or they'll raise prices by that ten percent and become the marginal supplier. No way they're going to accept a loss. (Many items shipped into the USA of late have tariff related fees.)