Something doesn't pass the smell test here. Why would it cost 3X more per student in Somerset County? Are the kids triple-masking in that county?
The key word is "enforcement". The masks themselves cost bupkis; it's the cost of whatever enforcement they're doing that jacks up the price. And that is so subjective and could be anything someone to sit in classrooms and monitor; to the people who create posters to dot around the school; to the "consultant" they hired (usually a relative or someone else connected) to "train" the teachers in proper mask wearing.
You can ask the school board exactly what that money was spent on, but I doubt you'll get an answer.