Note that $15k isn't tremendously more than public school costs:
> Total expenditures for public elementary and secondary schools in the United States in 2013–14 amounted to $634 billion, or $12,509 per public school student enrolled in the fall (in constant 2015–16 dollars).
That's relatively high, but local conditions vary.
Note that many Montessori schools offer access to financial help. The key benefits are said to be derived between the ages of 3 and 6. My daughters both started at age 2, still going, I wish I had had that kind of education.
Say it's $15k per child per year, and we're talking about a preschool. That means state mandated teacher ratios, depending on the state. Let's say it's 1:10, and that's on the low side. Suppose you have two classrooms of 20 children each. That means you take in 300k in tuition and you have to pay four teachers plus at least one administrator. Knock off 100k for rent, overhead, insurance, certifications, capital expenses. That leaves you with 40k for each teacher's total compensation. How far does that go where you live? Realistically, most preschools charge even less and pay their teachers accordingly.
You are correct about the multiplication, I forgot to multiply by two classrooms, but let's keep my other assumptions. Start with $600k. Subtract $100k for insurance, rent, and overhead. (And I think $100k is a low estimate here.) Now you have $500k and 5 employees. That's still $100k in total compensation per employee. It's not dire poverty like my $40k estimate before, but keep in mind that that's still a good deal more than their gross pay, which will come in more like $60-80k once benefits are accounted for. In the kind of area that can support a $15k/student/year Montessori school, that kind of pay is basically decent, but it's not like they're laughing all the way to the bank.
