mexican toll road expenses?

We have found that on every trip to Mexico, we have spent almost the exact same amount on tolls as we do for fuel. Figure you fuel cost, mileage from google maps and fuel cost per gallon roughly the same cost for fuel as in USA tho it is a little cheaper, and that is what we budget for tolls. You don't save anything in fuel cost to travel in Mexico when you add in the cost of tolls. There are free roads but most of the time we take the toll road, personal choice. There are a few free roads worth taking but not many when there is a toll road. There is a site that maybe someone will post that has the toll charges but in Spanish last time I looked.

rocmoc n AZ/Mexico