alt Hacker NewsLol DigiKey has been itemizing tariffs for years. They're not "giving up" any money; it's literally an extra line item on your invoice.
For the same reason when small local businesses charge you a 3% service fee to use credit; they're not giving up that money because you wouldn't have been charged it otherwise.
If you read the article, you'll see the paragraphs about all the paperwork to set up a FTZ, the delays in fixing broken/changing tariff calculations, and the fact that some of the other parties involved simply aren't paying their share of the costs. All of those affect digikey's costs.
The parent's point also applies to the companies buying product. Every dollar they spend on tariff line items is another dollar they're not sending back into the economy via expansion and wages.