In the US, school buses are typically 70-80 seaters; when I was in high school ~4 years ago, I rode a Blue Bird Vision (https://en.wikipedia.org/wiki/Blue_Bird_Vision). These will get around ten miles to the US gallon of diesel and cost around $110,000 US. The lifespan of these buses is typically around 20 years; each school day, they might be driven a hundred miles or more. $1m over 20 years seems reasonable.