Some people think that just because it's not a lot of money, it doesn't matter that you are spending it. Well, it doesn't work like that!
If your coworkers and manager pressured you to pay $15 a month for coffee and snacks to be available in the office kitchen, would you do it? And what about if you didn't eat that food, would you continue to pay for it just to avoid conflict? Do you see reason to continue giving money to the cause if you aren't going to eat said food? I don't think so. This story had a lot of things that didn't sit right with me, but let's analyse it one by one.
The first thing that seemed very weird to me was the fact that employees had to pay for coffee and snacks to be available in the office kitchen. I kinda understand it with the snacks, but coffee? I have worked in different offices over the years, and no matter what the job was about, how much they paid, or how many hours I had to be at the office, I always had coffee and water (hot and cold) available any time I wanted. It was never something that I had to pay for; it was there. At one of the jobs that I had, we had available food and snacks. We had protein bars, fruit, cookies, all for free. It was just a custom of the workplace. I understand that not every place can provide the same thing, but to charge for coffee is just too much. That should be simply available for all employees, no matter whether they pay or not.
Another thing that I don't understand is why they do this collective purchase of food for the office; isn't it simpler to just bring your own snacks from home? I would prefer a thousand times to go buy the protein bars that I like instead of having to hope that there are still the chocolate kind available in the kitchen. You will pay for it anyway; why don't you just bring your own stuff?
And the last thing that completely strikes me is the fact that the other coworkers are so mad that this employee stopped contributing. This employee brings their food and snacks. They don't need anything from the office kitchen, so why bother to pay for something they do not consume? And what is so bad about losing $15 a month? They said it was almost no money-wise, so why do they care so much that they are not going to count on that amount anymore? Also, prohibiting this person from even accessing the office kitchen is crazy behavior. That is going too far over a dumb dispute that shouldn't be happening at all.
In conclusion, if I were in their position, I would have stopped contributing a long time ago and simply buy what I like to consume in the office, but also, I would notify HR about the behavior of the coworkers. They were too defensive over something with zero importance. As they said, it's just $15, so why make a whole deal out of this employee refusing to pay it?