The article and follow up comments addresses that. As an example when talking about just the box the game comes in, "the quotes I’ve gotten in the US–even from companies that specialize in making boxes–are literally almost the cost of making the entire game". He also mentions that some of the machines needed to make certain pieces don't exist in the US and would have to be imported from China, and thus you'd have to pay tariffs on the machines.

He does mention that he's started to think about fundamentally redesigning his future games in a way that makes it possible to cheaply manufacture and package them in the US.