Over the years I have met many people that are happy with Mexican dental work. They all did their homework, and got recommendations from fellow traveler's prior.
But my 2c's on the topic is it's like buying a used car off a lot. If the car says "with warranty" expect to pay more then for the same car with "as is" on it. IMO that is the price difference between the two countries.
One lady I know I think has it figured out pretty well. Once a year she gets cleaned and checked in the US. Her long time dentist looks over all her Mexican dental work, and then sends her home with a clean bill of health. He knows she's on a fixed income and is good with it.
Thereโs no fool, like an old fool.