I have been reading on this subject for the last couple of hours. Apparently, no one knows exactly how the tariffs will be administered, or even determined. As is with all things to do with trade it is quite a mess and enormously complicated. According to the NYT, there will be study groups that look at different countries and their metal exports and then will make a determination of what the percentage of tariff will be.
I couldn't find one thing about whether or not it applied to finished goods, goods that have a predominance of steel or aluminum in them, bulk raw stock, specialty metals or blends, etc. So I think at this point any ideas of how that will specifically affect the knife culture is just speculation.
My concern is that if (as this did under Bush the younger) goes to the WTO and found to violate international law binding fair trade, then other countries can retaliate as they see fit. So even if the tariff only affects raw stock, they can still raise prices on everything they sell (including knives) if this tariff is found to be illegal. I am more worried about the blowback and retaliation from the international community than the affects of the steel/aluminum tariff itself. The cost of our knives (of which many have just jumped in price a great deal) can go up exponentially because of trade tariffs on them imposed by other countries for any other grievances they might have, not related to cutlery.
If the tariff is applied to the steel, and only the steel and no other sanction/tariffs/fines/VATs etc. are considered it will be as Frank (knarfeng) says a simple arithmetic equation directly based exactly on the amount of steel or aluminum used in a particular knife.
I don't think it will be that simple and history has proven that it won't be. Most economists believe that this could get nasty for all of us that buy knives (and a host of other goods) not for a tariffs on the steel, but for the tariffs, sanctions, etc. that are sure to be launched on all goods as retaliation. I think a more realistic take on this situation would be if we put a 25% tax on steel coming into the United States from Germany, we might be able to expect a VAT (like England has) with a variable percentage of the value of the product, not its components like a steel blade or aluminum handle. In other words we might be looking at a 15% (or much more) tax on a finished knife (or more) rather than a tariff on one of its components.
Robert