I don't claim to know what the fair price for the .com registry. I will say this though the hosting isn't free. There are millions of requests per second across all networks from all across the world. They must respond with low latency. The major registries are nearly always under DDoS attack. There is a reason verisign has some of the best DDoS protection.
All the data centers across the world, the network connectivity, the DDoS hardware, servers, custom software and staff to run it all must be expensive.
All the data centers across the world, the network connectivity, the DDoS hardware, servers, custom software and staff to run it all must be expensive.