Client Lunches & Expectations

So many of our jobs involve entertaining clients. What is a typical rule of thumb that you use on how much you should spend when taking a client out to lunch? I had a friend that took a client out to lunch, he got there before her and let her know that he ordered a bottle of wine. He also left before she did and when she got the check, the bottle of wine was $900 ! She said she almost cried and wasn't sure how she was going to explain this to her manager.