Symbolism, Imagery, Allegory
El Patrón likes his stuff, and it's not hard to understand why. The more stuff he has, the more powerful and important he seems. He even decides to be buried with all his "belongings," including the people he owned and controlled, like some pathetic, materialistic old king.
But not every character is as greedy as El Patrón. Celia, for one, has just a few prized possessions, including her chipped Virgin Mary statue, which "she had brought […] with her all the way from her village in Aztlán. The Virgin's robe was slightly chipped, which Celia disguised with a spray of artificial flowers" (2.80). The statue isn't much to look at, but it's got sentimental value for Celia. We'd like to think that instead of hoarding it after death, Celia will pass it on to Matt, so she can pass on those memories. She's got the right attitude when it comes to stuff: don't value everything; value things with meaning.
Unfortunately, the meaning of material belongings can sometimes be a bit foggy. It takes Matt a while to understand what's important, because El Patrón's greedy ways have had an impact on our hero. When El Patrón gives him a gift, the narrator tells us, "Matt was too old for such things, but he knew that the [toy] car had been very expensive and therefore El Patrón loved him very much" (11.64). At this point, Matt's still a pretty young dude (despite what he may think), and he thinks that El Patrón loves him simply because he bought him a pricey toy. In Matt's young brain, a gift equals love.
As he grows older, Matt realizes how meaningless material things can be. He leaves just about everything behind when he flees to Aztlán, and when he returns to Opium, he cherishes the items that he connects with those he loves, like the supplies Tam Lin left him at the oasis. What matters here are not the things themselves, but the people they have come to represent.