I think the reason you don't understand how things work, as far as toll roads. is because you can not see any numbers.  Since many are privately held companies who basically own the toll roads for 3 decades, it is not required information for the public.
 Not being able to see numbers, or the half mile back ups like you regularly see at the US toll roads's  plazas, it is hard to accept the fact that money is being made. You do need to keep in mind that these types of projects are financed by banks and in part by Mexico.  It is a 30 year investment in which everyone expects to get paid. 
  The second phase, of a two phase project, was just awarded to a company from Portugal.  This toll road will link Tampico to Veracruz city. Both ends are in place plus the major interchange at Poza Rica/Tuxpan. All is needed is to connect the dots, a couple bridges and, except for the area around the nuclear power plant, mostly flat. Building, maintenance and concessions are for 30 years with Mexico financing 10%.