Here in Costa Rica we have just one state owned monopolist cell phone provider (until now). This service provider is not allowed to make a profit. For that reason a regulation authority has to approve the tariff for any service, based on a cost calculation provided by the service provider.
Even though all the equipment for infrastructure has to be paid in Dollars here, we enjoy relatively low tariffs: less than six US-Cents for a minute of call nationwide, regardless if mobile-landline, mobile-mobile or landline-mobile. Only outgoing calls pay, of course, tariff at night and on weekends is even lower. An SMS cost less than a mind boggling third of a US-Cent (exact $0.0029). Internet over cell phone – only GPRS with EDGE – cost $6.75 a month flat, no limit. All prices at present exchange rate, VAT included.

This may illustrate how low cell phone tariffs can be when profit margins are cut out. The downside is, that the service is far from being competitive. It lasted much too long to install, some areas still lack coveridge, number of lines was very limited until recently, 3G is said to be under way, may be available by begin of next year, but I need to see it first to believe it.