Hi Navegator: You left out Mexican citizens and expats who were importing cars legally into Mexico ( not border areas). This big business. Some come from as far away as New York state. Even by car carrier. Before they had to be 10 years old and be NAFTA cars. But then a moratorium was declared due to corruption
( surprise). Most people were using agents and some of them provided Aduana with forged papers. I understand it was mostly at Texas crossings. But all the rules keep changing and the fees are really high. I have never checked but have read it can be 50% of the value of the car. Used to be just the IVA and a few$$$. Being an election year the importation may begin just before or after the elections.
Moisheh
