That makes a lot more sense. It would be a lot better if the DNS provider said something like, "First million DNS entries served is free, after that, we charge you $0.50/million queries" (Amazon pricing for DNS)

Then, you respond to every request as fast as you can. (Note, this also provides an incentive to the customer to jack up the TTL on the resource records, so 99.99% of the requests are handled at the caching servers instead of GoDaddy)