Goblins, Kobalds, Orcs, and other similar humanoids, have a set of primal motivations which serve to shape their behavior. For one, they live short lives and breed like cockroaches, so they are far more likely to be reckless and aggressive.
Upon reaching sexual maturity, they are driven by their primal instincts to breed, as often as possible. However, in order to obtain breeding rights, they have to compete fiercely against their fellows.
Winning trophies in battles is a key element of impressing the females of their species, as well as rising up the social dominance ladder in their own clans. Luckily for humankind, most of their energy is focused on battling each other for dominance.
Once these humanoids are past their physical prime, they are quickly victimized by their younger competitors seeking to claw their way to the top of the social ladder. They never live to see their grandchildren.
The most beautiful and dominant among the females are fought over by the males, and taken care of in their breeding pens. Females rely upon the males to bring them food. They also never live to see their grandchildren, as the males cast them out after they are past their physical prime, once they are no longer capable of heavy breeding.
Gold and jewels are collected by the humanoids, but they serve no economic purpose as humans would define it. They are used solely to gain the loyalty of females mainly, and other males secondarily.
The "Goblin King", for example, would be decked out in all manner of trophies taken from humans, animals, and monsters. He would rule over his fellow Goblins with bullying and displays of dominance. He would gain temporary allies and female mates by dispensing gold, jewels, and other bobbles. His inferiors would continually come to him, plying him with gifts, seeking his favor. Occasionally, he would have to fight off a challenger seeking to usurp his position. Eventually, he will be overthrown.
Because of the breeding rights afforded to the "wealthy" goblins in their lairs, young goblin males are propelled outward to maraud their way to some kind of wealth and stature. Young goblins will form raiding parties to assist one another in their common goal of acquiring treasures and trophies. However, there is no loyalty among them, and no sense of honor. The weak and damaged are left to die without a second thought.
In Arizona, Goblin society is centered in the mountains to the north of San Carlos Lake. Kobalds predominate in the area of Yuma and infest the lower reaches of the Gila River upto Gila Bend. Orcs dominate the area east of Alamo Lake and north of the Santa Maria River.
There is often great wealth to be found in humanoid lairs, because it is perpetually brought in and hoarded in their breeding pens. Because they do not participate in a trading economy as we know it, their wealth rarely comes out of their lairs. Usually, it is never to be taken out again until it is ripped out by force, following much slaughter and conquest by a superior race.
Thus, the wealth of the Goblin King is a subject of great legend, and many a human adventurer has made himself wealthy devling into the Goblin Caves.