It was my rough estimate, from looking at both years ago. You do have a higher monthly payment, beyond shared expenses, but that varies greatly depending on things like how much debt the cooperative has.

Housing cooperatives (wiki) are quite great. Where I’m from they are rather common, but unfortunately the ‘buy in’ costs have increased a ton in the last couple decades. Even then, paying e.g. a third of what a comparable owner apartment costs, still makes it a lot more affordable for many people.