If US guns would be uneconomical enough that cartels would not want them, then who supplied the money to shop at the Lone Wolf WMD Flea Market?
A lot of it came from the FBI, in money to a confidential informant, to buy the guns. It is one reason for the coverup. There was also a third rifle at the Brian Terry shooting, that was taken from the crime scene. The word is that it was tied to this confidential informant, which is why it "disappeared" from the crime scene.
We did with our tax dollars?
I’m not sure why they bought them. Maybe it was just an opportunity - an impulse buy?
Lets put it this way - where, in the US, can you buy an automatic weapon of recent vintage, a grenade or heavy weapons?
We might have some stuff they would want (Barretts?) but they can get the M16s from our “allies” and AKs from the USSR’s former clients or Venezuela.