According to a Mexican friend of mine the mordida to driving without a seatbelt was now $100mx. The Transito officer just wouldn't take $50mx
For $50 pesos he wouldn't budge and insisted he would keep the driver's license so that he could pay the regular fine at the station in order to get his license back.
I could only guess that with the extra paperwork and administrative fees that would entail it would cost a bit more to go down to the station and pay. When you figure in the time and travel involved in going through the "proper channels" it just does not make it worthwhile to do so. Mordida is wonderful in its own way.
Gone are the days when $20 pesos would take care of most any minor violation. Around my street corner is a gaming place for video games, foosball, and pool tables. The kids hang-out there at night and sometimes get noisey so there have been some complaints and things have settled down now. Rumor has it that a few months ago a police patrol rolled-up on a drug transaction, some cocaine supposedly. The kid's father showed-up and managed to convince the officers it was a non-issue. Seems he paid about $800mx to make everything go away. This is all just hearsay, mind you.