An outstanding article. However, I'd love to understand further the business dynamics of handling a price increase for a service. Five years ago I somewhat went through the same scenario..except we went from a donation model to a subscription model. Now it is time to evaluate a price increase and up against a five year established price I'm curious as to how it has been handled in the past.
I think the most of the tips apply to price increases as well. Most of your loyal customers will understand that prices go up over time, but if you communicate with them and explain the changes, offer some grandfather'd benefits, etc. etc you'll find that many will make the transition with you, especially if it's gradual.