The head of the Catholic Church aka. The Pope is privvy to millions of dollars of the Catholic chuch's money and travels around the world with it - he is head of a multi-billion dollar religion centred from one of the world's richest cities - The Vatican - this may explain why he preaches for free. He delivers sermons, which is not what I consider the Dalai Lame to be doing
The Dalai Lama is a religious leader, he is a teacher, a spriritual leader of Buddhism. Buddhism is not a religion, it's a spiritual frame of mind - you can be a memeber of any other religion, believe in any God and still follow Buddha's teachings. The Lama is not from a wealthy state, nor is he even welcome in his own home currently - and so he travels spreading the good words and trying to help his people. That takes money,money to rent a venue to hold all the people that are interested in going to see him (if only 5 people wanted to attend the venue would be small and the tickets would be cheap) money to staff the event - and the rest of the money earned goes towards his cause of freedom for Tibet <---- you know, the place he lives in exile from because of Chinese rule.
The teachings of Buddha are free and available in local groups, word of mouth on the internet and countless library books. The Dalai Lama's words and teachings are available in his books which can also be obtained for free in a library -
Need to know more?
Check out his website
http://www.dalailama.com