If you are an individual who mostly keeps to yourself, then you will save money under the new pricing, but it's a tough move for agencies and projects that rely on contributions from the community (but wish to maintain private repos).
Of course, others rushed to capitalize on Github's announcement — Gitlab in particular.
Github needs to make money, just like any other business. I'm sure they did a lot of analysis before making the change. And users will get at least a year's worth of notice if they decide to force the change for all users, as existing users are (for now) grandfathered into the old pricing.
Github may backpedal on this at some level, but in the meantime some aren't waiting and already thinking of where they might be moving to.