Oh, no. The cost wouldn't be a consideration. I was just exclaiming in general at the cost (we price those claims at work). !!!
No, she'd call the parents because their hemophiliac son had a bleed. It's information they need to know. If he was infused at school he may need less factor at home this evening. They might need to follow up at home, or with his treatment center or with his doctor. Also, they now need to send in replacement Factor VIII or IX.
At Sixteen years old, and if you really need to for your plot, it's conceivable the school nurse might write a note to the parents instead of making an actual call. Especially if she tried to call and couldn't get hold of them. The kid is self-infusing at home and could know enough to re-calculate his dose that night, and take another vial in a cold pack to school the next day. But as a reader in the health care industry with a school nurse in the family, suspending my disbelief that she wouldn't call the parents would be an uphill road for the writer.
ETA: You may already know this, but for infusion: Alcohol wipe, followed by infusion of saline, followed by alcohol wipe, followed by infusion of Factor VIII, followed by alcohol wipe, followed by infusion of saline (and in this case, definitely NOT followed by another alcohol wipe and an infusion of of heparin.)