[Cactus Jack]

To add to the post above:

Should have said that this is the only case where the ransom note was written inside the home and left in the home with a dead body.

The ransom conversion to Mexican pesos was something that someone outside of law enforcement mentioned and seemed to be coincidental. John's company had some type of financial event (can't remember if it was having given Christmas bonuses to some employees, giving raises only to management, or firing employees) and the most prevailing thought is that the figure in the note relates to this (whether from an employee or from someone who would want to make it appear as though the note was from an ex-employee).