How much are hair extensions, and shouldi get them?

Ohkay, here's what'sup. I'm half black, and I'm constantly straightening my hair. Sooner or later, it's gonna fall out. I can't stop straightening it cause my hair's a LITTLE past my shoulders, and it takes forever to grow. So; I'm thinking extensions, cause i think they're adorable. I'm thinking about to a little past my . I'd kill for them. Should i get them? What am i supposed to do?...