Any industry that makes money will tend towards this in one form or another. This does not mean that there are no competitors or independents not making money - it merely means the vast majority of the market is consumed by a few companies/brands who set the prices and keep price floors.
Bread is an example of a cartel structure reinforced with marketing, economies of scale (monopoly) and previous consumer buy in. You can choose from multiple brands - but you'll notice the price of bread isn't falling very quickly - it's an implicit pricing pact - you can undercut your competitors - but not for long, and definitely not forever.
Oh, I see you're using a definition of Cartel that's rather different than the standard one[1]. If you just mean that commodity producers more or less converging around a price without an explicit agreement between them to inflate that price than of course every commodity ends up being a "cartel" and you'd have a hard time finding an economist who would disagree with you.
Bread is an example of a cartel structure reinforced with marketing, economies of scale (monopoly) and previous consumer buy in. You can choose from multiple brands - but you'll notice the price of bread isn't falling very quickly - it's an implicit pricing pact - you can undercut your competitors - but not for long, and definitely not forever.