GMAT scores alone definitely do not carry the weight of your business school application for the top schools, i.e. they will not guarantee an interview or admit. As far as I understand, GMAT scores are something to be "checked off." A high score is required to be considered, but it's just one of several hurdles.
Extra curricular activities and a good GPA are also a must for the top schools. If you have a good reason as to why your GPA is low, however, you can explain it in an optional essay.
That being said, I can't say if it's worth your time and money to apply, and it's not just because I don't know how much you value your time and money! If you can write some stellar essays, you'll obviously have a much better chance. It's all about how you present yourself, and I can't say whether or not you'll have a compelling application.