Hiya.
Don't worry; it's not going to run you $150/school. The $150 is the "processing fee plus one school" kind of thing. When you add another school, it costs an extra $50 for a total of $200. Add another school and pay approximately $45 extra for a total of $245, and so on. I'm not sure about this year's rates, but each additional school you add will run you less than the previous.
However, if you ask for your app to be transmitted to additional schools AFTER it's been processed, those schools cost $50 each.
Good luck!