I agree with Yada...
Only time I ever did something tantamount to paying for a lecture was to meet Salman Rushdie because I worship him... it was very much worth it...I had to buy the book ahead of time and Politics and Prose and they gave me two tickets to go hear him speak at 6th and I.. after the speaking we all got in line and were able to meet him, say a few words and get him to sign a book or two..
at some point it became ok to charge people as part of your promotional book tour.... and obviously people have too much money..