This. $200 for 4 months for 25 users works out to $2 a month per user. You could double or triple it and still be less than the personal plan.
Those large multiuser plans probably come out of grants, departmental budgets, etc. So they're likely not all that sensitive to price. Pretend you were still in academia, and had found online some great cloud-hosted software you wanted to use in a course, would it change your / your department's decision about purchasing that software if covering 70 students for a semester cost $400 vs $800 vs $1000?
Those large multiuser plans probably come out of grants, departmental budgets, etc. So they're likely not all that sensitive to price. Pretend you were still in academia, and had found online some great cloud-hosted software you wanted to use in a course, would it change your / your department's decision about purchasing that software if covering 70 students for a semester cost $400 vs $800 vs $1000?