Not enough!
Last year I think I saved some money by training on a Friday evening instead of going straight to the YC for a drink. I also felt safer as the other members could keep an eye on me as I have a tendency to capsize. Previous to this we have employed John Pierce who has kindly given his time free on some occasions and charged on others. This coaching was carried out on weekends so the monetary costs were reasonably low. Prior to the A Class Nationals there was a coaching day. Chris didn't charge for his services but it did cost in a days lost income. I really enjoy the opportunity to be coached by top sailors, listen to there ideas and try and emulate them on the water. If I had more money and time I would probably seek out more clinics with various coaches.
The Dart Worlds are being held in the UK (Weymouth) this year, there are at least 4 Darts entering from Mumbles YC so I have offered to help them with some training. I am no coach but I can take a Committee boat out set a very small start line and do lots of starts, OK 4 cats on a starting line doesn't compare to around 150 but the principle of being in the right position at the right time does, you don't want 150 Darts in front of you on the first beat. So to some degree it doesn't matter if you just pop out on the water for an hour by yourself or employ a Pro for a day, improvements can be made, they just seem to happen a hell of a lot quicker when you are paying for somebody who knows what they are talking about.