I had a boss when I was quite young and green who played a game with all of the junior managers, it went like this. If you walked into his office and said you wanted to ask him a question he would stop you right there and ask you if you had a dollar bill (this was a while ago when a dollar would actually buy you something). You would of course say yes and then he would ask to see it, so you'd pull a dollar out of your pocket and he would say something along the lines of 'Yes, that's a dollar, just set it on my desk in front of me'. Then he would lay out the rules:
If your question was not very bright and if you could have come up with the answer by using your head for more than a hat rack - he kept your dollar but would answer your question.
If your question was a good question but you had asked him this question before and had just been too lazy to bother to remember the answer he had already given you - he kept the dollar and reminded you of his previous answer.
If your question was a good question and his superior experience and knowledge were now called into play, experience and knowledge that he had paid dearly for over the course of his career - the he would give you the answer and you kept your dollar.
Knowledge is not free, it is hard earned and should be valued as such.