When groups band together to control the supply of a product for their best interests, that’s called a cartel. If you and the other kids running lemonade stands form a cartel, you can force up the price of lemonade.
The word cartel originally referred to political parties that joined forces to promote a common cause. Over the years, cartel took on a decidedly negative connotation, and now it’s more likely to describe organizations that join together to limit supply of a product to force prices to remain high. You might read about an international drug cartel or a cartel of natural gas producers. To correctly pronounce the word cartel, put the accent on the second syllable: “car TEL.”