I am so thankful they don't do things like this here. There are high school dances, but no biggies, until you actually graduate from high school. So only one dress is required.
My grad dress cost ... $0 - yup, nothing. I borrowed a dress from a friend's older sister. I was a single parent by the time I graduated, and I couldn't afford anything fancy, so my friend's sister gave me one of her old dresses (she had two, one for the dinner and one for the dance, she purchased both herself), and did my hair & makeup for free.
I do know that I will allow Jenna to spend up to $100 this year, for her dress & shoes, for her elementary school graduation (it's kinda a big deal here when you leave the elementary school for the high school).
And when it comes time for her actual high school graduation, there will be a $200 limit from us, for the dress.