Answer:
They think material wealth (money) is all that matters.
Explanation:
According to the excerpt from "The Harvest" by Tomás Rivera, there is a discussion among two people about Don Trine, a bachelor, and from the way their conversation goes, it seems fairly certain that they plan to rob Don Trine because they believe he has worked for many years and as such has a huge amount of money hidden somewhere..
Therefore, the inference that can be made about the boys, based on this passage is that they think material wealth (money) is all that matters.