There is something magical that happens in the 100 pennies between 99 per hour and 100 per hour, a mental chasm that is in reality no different than 98/hr vs 99/hr but we make it into a big deal. Why he chose that number, and why people choose any number for an hourly rate is always a curious thing to me. We pick numbers that we think are palatable with no real regard for the same rigor we put into other processes. Has he tested his rate?
But the idea of hourly rates is accepting of the premise incorrectly...
My guess is that if he is truly great he could make some lawyers jealous. Charging $700/hr may seem far fetched for a developer but making 700/hr is a very different thing. 70K bill to a client for something that took 100 hours to make is a much more salient strategy if you give them what they want.