I’m not sure exactly what argument you’re making here, but if you want the sticker price to double when the tariffs equal the import price then you need one of three things: 1) imports directly to consumer, 2) every cost must be in direct proportion to the imported cost, 3) someone must end up with astronomical margins.
1) makes up a tiny fraction of trade. Case 2 is obviously unrealistic. I will lay out a simple example for case 3: WidgetCo sells a widget in partnership with MarkCo for marketing, InsCo for insurance and JungleCo for warehousing and shipping.
Widget costs $10 in China and shipping to the US warehouse is $2. Marketing is $8: 3/4 fixed costs and 1/4 commission based. Shipping from US warehouse to the customer is $6, warehousing costs are $2, and insurance is $1. All the company’s other internal expenses are 15% of imported widget cost plus $1.50/widget totaling $3 per widget. That totals $32/widget and they sell for $33, a 3.0% net margin or $1 net profit per widget.
Now, let’s imagine that tariffs have just increased from 0% to 100%. Shipping and warehousing are fixed costs. Being generous to your point, let’s say marketing commissions and insurance are calculated on the imported price (which is unusual.) That brings the new cost to $46.5, with a retail price of $47.95. That’s a 45% increase, nowhere near doubling. If you want the price to double, you will end up with astronomical margins. InsCo’s margins remain the same, but WidgetCo now takes $8 per widget, of which $2.05 is additional pure profit. Net margin is now 7.3%: (1.45+2.05 or $3.50 per widget.) 2.35x the net margin in a competitive industry? You’re toast, buddy. But it’s far worse for MarkCo and JungleCo. Both MarkCo and JungleCo are now raking in $16 for work they used to do for $8. If their net margin was 10% before, now it is 55%.
Now, it’s worth pointing out that the numbers in this example are quite generous to your point. In reality, most products are not sold for three times their Chinese factory cost, and many products have (legitimate or not) processing steps in other countries, or steps which could be easily relocated to other countries, which is of course what happened with the first Trump tariffs.