Cost of living in Rennes (France) is 77% more expensive than in Zapopan (Mexico)
This comparison is lacking data. It provides a decent comparison, but it is not yet reliable. It is based on 516 prices entered by 40 different people.
For example, you would need at least Mex$ 88,405 (€3,687) in Rennes to maintain the same standard of living that you can have with Mex$ 50,000 in Zapopan.