Matt loves nike. not only does he own ten pairs of nike sneakers, his entire wardrobe is made up of nike clothing. he owns t-shirts, socks, hats, and athletic pants, all with the nike swoosh. matt's obsession with nike can best be described as:

If MAtt is obsessed with Nike then he is a loyal customer of Nike and won't switch to another. There is a term used for this in Marketing called Brand Loyalty which says:
Brand loyalty is defined as positive feelings towards a brand and dedication to purchase the same product or service repeatedly now and in the future from the same brand, regardless of a competitor’s actions or changes in the environment. It can also be demonstrated with other behaviors such as positive word of mouth advocacy. Brand loyalty is where an individual buys products from the same manufacturer repeatedly rather than from other suppliers. Businesses whose value rests in a large part on their brand loyalty are said to use the loyalty business model.