How much did you pay your staff for the extra work, your banker for the extra time your money was tied up, and your customs broker for their in-bond services? (insert gentle sarcasm emoji here).
I'm not saying that it can't be worthwhile to go to the extra effort of doing your own importation. I am saying that US (and Canadian) retailers and distributors incur real and substantial costs when they bring in photographic products for sale, and that the difference in price is not just "markup".
There is a very real possibility that the sellers in Germany are making more profit on their sales than the US retailers are.
At the risk of repeating myself: "The cost of the film stock itself is only a small portion of the total cost."