A special separate dedication, a signed copy of the book upon publication plus signed copies of 10 randomly selected editions of Mondo 2000, High Frontiers, and/or Reality Hackers plus a monthly "newsletter" featuring particularly interesting and carefully edited content from the private discussion, along with a personal email letter from R.U. Sirius, quarterly, pre-publication.
Pranks for the investment! Insert yourself into our history.
Entry into the private conference, plus the opportunity to completely invent and write up your own Mondo 2000 experience stories and have them inserted (with editorial help and discretion) into the publicly available content. Plus all of the above.