On our Radha Damodar Party, we decided to use incense packs to get the person warmed up. A person would buy a pack of incense, and then we would give them a book and ask for something further. I told Prabhupada that generally we gave about four packs of incense for a dollar, and on the fifth pack of incense, we gave a big book, plus got a little extra money. Each time we gave a pack, we gave a Back to Godhead. Prabhupada said, “Oh this is not good.” He wrote a letter to Rameshvara saying this should be stopped. I happened to show up that day in Bombay to take my turn as a GBC secretary. The previous secretary, Hansadutta, told me that this letter was going out. I rushed to Prabhupada and said, “Srila Prabhupada, I don’t mind, but I have to say that our book orders are going to be going down about fifty percent.” Prabhupada stopped. He said, “Are you paying the book fund?” I said, “Not only are we paying, we always have a credit.” Then he called his secretary back and said, “Destroy that letter.” He said, “Never mind. If you’re paying for the books, it’s okay.“
Reference: Memories Anecdotes of a Modern Day Saint – Volume 2 by Siddhanta Dasa