Just made the trip yesterday and the tolls, starting from the Macroliebramento to the Rio Grand river in Laredo.... going through Lagos de Moreno, bypass SLP on the west, through Saltillo/Monterrey...... was a staggering 1320 pesos! That's about $71US @ 18.5 exchange rate.
I usually go through Aguas/Zacatecas/Saltillo/Monclova to Eagle Pass which has FAR fewer tolls and the roads are just as good.
BTW, about 3km short of the border in N. Laredo got pulled over by mordida -seeking Transitos. I'm used to this with my US plated car around both N. Laredo and Colombia crossings. Short story is that I did NOT pay them, asked for a ticket and through their frustration with me, told me to Vamoose!