How does paying 35 dollars for travelling 150km on a toll road strike you ? How many tanks of gas do you burn in that distance? This is not an untypical fee for ceretain toll routes, bu t they do vary.
For a more actual set of figures you can buy one of the GUIA ROJI Roadatlases of Mexico and in the back (of my2004 edition ) there is a schematic layout of all the major toll routes with markers for all the toll booths , PEMEX stations and other stuff along the way and the toll prices for cars , same as a bike ,as well as for trucks and buses.You can also find a website for the toll highways of Mexico with this data.
If you study this road schematic you may be able to dodge the toll booths by getting off the toll road just before and rejoining a short distance later. Keep your eyes peeled for signs that tell a toll booth is coming up, i.e. they will indicate the LIBRE route splitting off, usually before a town or city. Also watch for points where a lot of trucks and cars suddenly peel off the toll route and note where they are going. This is a good way to find the roads that the locals use to avoid the toll booths .For example at Guaymas the toll route Mex15D splits off onto a well signed new route to the east to bypass the city about 15km north of the actual town. Just by taking the Libre through the city you miss the toll station , save the cost of a tankfull of feul or more and it doesn't add significantly to your travel time.

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http://advrider.com/index.php?thread....207964/page-5 then scroll down to post #93