Class prices are increased according to many factors. When classes do go up, we give the members at least 30 days notice of the increase and include a statement as to why. Things like increased overhead, instructor pay raises, etc.
My personal training clients are on an entirely different rate system. When my rates go up, my long term clients are one rate hike behind. That is, if my new client rate was at $60 dollars and the new rate is going to $65, my long term clients were probably at $55 and now go to $60. My long term clients always are at a lower rate. It is part appreciation and part client retention.
I directly tell them that my hourly rates will be increasing by so much and give them a date at least 3 months in advance. Then I ask them if that would affect their ability to train with me and negotiate how much extra they could afford if that is the case. They really appreciate that I am willing to work with them especially if I know they are on a tight budget in the first place and really value my service enough to pay more.