The bands are sporty and differently designed. Apparently they match some of the most popular sportswear aesthetics Nike has. But if you still want to frame it

The bands are sporty and differently designed. Apparently they match some of the most popular sportswear aesthetics Nike has. But if you still want to frame it as "paying for advertising a brand" you could look into the ways that people use brands to say something about themselves. I recommend reading about the success of Starbucks, Ferrari, and Apple, especially the first 5 or so years of the iPod. This happens in Frankfurt too. Adidas, Puma, and many more clothing companies in Germany are not cheap and display their brands prominently