Earlier quoted context omitted.
In this context "long term" is the time it takes for the market to respond by building more schools or housing or whatever, which generally takes a low single digit number of years (like one). To which the response then becomes, so what? And that's assuming your argument is true, which in general it isn't. If you raise prices then some of your customers will go elsewhere. That's why sellers don't raise prices already…
It feels ambitious to suppose an equilibrium state for schooling to be met within a year. I'd buy two or three. Is it the case that existing private schools have much excess capacity? Frequently the argument for private schools is smaller class sizes; a rapid influx of new students without new, excellent teachers defeats the purpose. Presumably new classrooms would need to be constructed and so on. If you receive a $…
Suppose you're right and a $5000 voucher will cause a $1000 increase in tuition for three years, after which new schools will open and the competition causes tuition to fall again.
So as a parent, for the first three years I'm up net $4000/year and $1000/year is going to build new school capacity to meet increased demand, and thereafter I get the whole $5000/year. Am I supposed to be unhappy about this?