Flowbox Tech Support interview questions

The interview process was smooth and clear, the company seemed to be exactly what I was looking for. There were 2 interviews - one to get to know each other and the second was a technical one. The third one was to get to know the people I was supposed to be working with. I wanted to negotiate the salary as what I was offered wouldn't allow me to live without being worried about each penny spent. The agreement was I will think about their offer and get back to them. I did, not only with the question of whether negotiating the salary is possible but also with some follow-up questions as I wanted to work there and hopefully agree on some salary that will satisfy both parties. I've attached 3 people to that email and no one got back to me... At all. That's unprofessional. I would understand if the answer would be 'no' but would be fair to at least send a short email with this information.