I'm not an Islamic scholar but this fireworks have never come up in any question or book I've ever read.
Fireworks are a form of entertainment - which is mubah.
Also, what about using fireworks on Eid? I recall a hadith (I'll find the reference tomorrow inshallah) where the Prophet (pbuh) said: -
"Entertain yourselves. For I would hate for people to think there is harshness in your religion"
Also, I don't know about in the US, but in Britain, fireworks are pretty cheap.
Yes, money could go to better places, but unless you live in a flat, with no wallpaper, wear no brand name clothes, have no uneccessary gadgets or toys, only use a computer when in college (where its free), don't own a TV, haven't bothered buying carpet for your house, then I think it's hyprocritical to say that buying fireworks are haraam.
I brought quite a few to set off on Eid, mainly for my younger brother and a few of his friends. They have no way to enjoy Eid properly - so why is it haraam for me to provide something for them?