Verisign did not take a risk by developing the dns system - network solutions did that.
Verisign maintains a perfect monopoly over the addition of records to a central database, with minimal operational costs. Their business is almost pure profit by operating a mandatory service with highly inflexible demand.
If they were forced to compete on providing access to a core internet infrastructure (e.g. allow competitors to also add records to the .com registry) the price would lower to the actual cost of providing the service, which for an update/add query, I suspect would be in the pennies.