$700/hr for legal advice vs. $100/hr for a top software engineer – why?

I'm currently working with a really great iOS developer. He is charging me $100/hr, which seems like a lot, but the hours he quoted for the full project were very reasonable. However, need some contractual work for the same company and have a friend who is a partner at a major law firm in the Valley & he charges close to $700/hr. He is very bright and hard working, but can anything justify $700/hr. What am I missing?