Was it for the "collective interest"?
You're overthinking it.
As mentioned before, this was Bai Lan's compensation to Class D.
It wasn't merely compensation for Bai Lan chewing out the others. It was also compensation for the serious violations he planned to commit in the future, which would cause the class to lose points.
Bai Lan knew that his future violations would cause Class D to lose points, so he had thought of a way in advance to help Class D preserve its score.
Others "killed to save life."
Bai Lan, on the other hand, was "preserving points in order to deduct them."
Bai Lan felt that, for a while in the future, he would have to commit frequent and serious violations in order to drop out. Since that would needlessly harm everyone else's interests, he planned to find a way to preserve part of Class D's score, then use his violations to deduct the portion he had preserved because of himself.
After adding and subtracting, there would even be a slight surplus.
That way, Bai Lan wouldn't owe them anything.
According to Bai Lan's original plan, he should have gotten into several fights in front of the cameras this month and then been expelled.
However, Bai Lan had miscalculated. He hadn't accumulated enough demerits, so he hadn't been able to deduct the living expenses he had found a way to preserve, allowing Class D to take advantage of him.
To put it modestly: of Class D's more than sixty thousand in living expenses, at least thirty thousand had been "saved" by Bai Lan!
To put it more arrogantly: judging from Class D's violations at the end of the month, if Bai Lan hadn't found a way to preserve their points, their living expenses might well have been reduced to