I imagine all of those regular blood tests would've made a huge dent on her family's finances, since while most blood tests in general are cheap, when piled up together they make for a pretty steep pricetag. Plus she has to do them on a set schedule made by the doctor. Still, her disease must be something pretty serious if it warrants the need for blood tests in the first place, since it looks like Hisakaki-sensei's trying to monitor something with her.