GP is referring to the registry, not the registrar. There's lots of competition between registrars, but the registries have a post-sale monopoly on all domains.

Put another way, as soon as you register a .com domain, the only registry that can sell you a renewal is Verisign. If there weren't price controls, Verisign could increase the price of a .com renewal to $100 and there's nothing anyone could do but pay it.

This whole thread back to the root is right. Verisign has a monopoly, you can never drop a domain once it's associated with your business, and all of it should be regulated like a monopoly.