Yes. The wealth and power of the cartels is testament to the fact that there is certainly a large demand for those sorts of things. But it is not limitless, and the cartels are subject to the laws of supply and demand like everyone else.
What IS limitless is the desire for wealth by the cartels. It is not credible to argue that there are billions of dollars worth of untapped criminal activity that they could be exploiting now, but for some reason are not.
I guess we disagree on that. There are limits to what they can do because there are only a certain number of people who work for the cartels. Decrease their 'workload' in one area, they can just increase it in another (or new) area. They can also just get more violent than they already are, trying to steal 'marketshare' from each other. They aren't simply going to sit back and lose revenue. It is naive to think they would.