It's relatively easy to make from ephedrine or pseudoephedrine, but the over-the-counter decongestant pills containing those precursors have had their availability drastically curtailed in the US over the past 20 years. I think that Breaking Bad showed how much hard work it was to have a bunch of straw-purchasers buy pills up to each person's legal limit, so you could gather enough of them to make wholesale quantities of the drug.

Cartels can run large labs supplied with drums of industrial chemicals instead of taking the "easy" but difficult-to-scale route that starts with OTC pills. And if they used to be able to turn a profit on smuggling product with a mass-to-value ratio as low as cannabis, they should surely be able to manage the same with methamphetamine.