A new monthly magazine which is coming out with its third issue has decided to use my crossword puzzles exclusively. Their second issue sold over 100,000 copies with expected growth rate to grow with every new issue. For now I'm giving them one new exclusive 15x15 puzzle every month for free, so I can get anchored in the magazine for sure and get name-exposure. However, when I do decide to set a fee, how much should I charge the mag per month to use my crossword puzzle? Anyone have experience with this?