How much are auto workers paid in Mexico?

The Washington Post reports that “The Center for Automotive Research, a Michigan-based think tank, found that in salaries and benefits, car companies pay an average of $8 an hour for Mexican workers, while in the United States that figure would be four to seven times as high.” A few paragraphs later it reports on a walkout at a Mazda plant where the supervisor was abusive to the workers, stating that “For a job with 12-hour days, often including weekends, that paid about $75 a week — with $3 of that disappearing into union dues — some decided it was not worth it.” Forget about the weekends, $75 for twelve hour days five days a week would come out to $1.25 an hour. That is a lot less than $8. To reconcile the two either workers would have to get about $6.75 an hour in benefits or there would have to be a very high variance in wages. It is possible that both numbers are accurate. One number is an average while the other refers to a particular factory. The large discrepancy does, however, raise a lot of questions that the author and editors do not even seem to notice.