Saw this posted on the other site and while geared to trail runners (it is a running magazine), reading into it other users are affected too, especially nonprofits advertising group trips (who already pay entrance and per hiker nightly camp fees).
http://m.runnersworld.com/trail-running-training/groups-running-the-grand-canyon-will-require-permits?page=single
Personally, I finished backpacking with nonprofit groups there several years ago and it helps to keep a group small. Most can easily split $179, but this may put off less wealthy users.