I've worked for multiple HR companies who performed studies, all of which showed that salary isn't the highest priority on employee concerns. Yet, in my experience, the number one reason I lose employees (or have left a job) was money.
Also, yes, I have poached employees from competitors by simply finding out how much they were making and offering more. You want to show me how much you are paying your people? It will tell me either that you are not profitable (if you are paying too much) or it will tell me the exact number I need to beat to take your best people.
And rest assured, I WILL take your best people.
Rest assured, I HAVE had my best people taken as well.
Business is not a democracy. Business is a competition. It is a fight for survival. No business is going to be so transparent to reveal enough to help their competitors. Even those 'transparent' companies who post on blogs their entire process? Trust me, they ain't showing you some of the most important stuff. They are marketing to you.
I don't know how this comment will be taken on HN, but I realized some time back that the number of people on HN who are smart is very high, but the number of people who actually run businesses is much, much lower. So I run a company. My comments are based on my experience.