Not to sound blunt, but you can charge whatever you feel you're worth. I've never had a client blink when I told them what my hourly rate was. They do a calculation in their head, but it is not "Is this too expensive?" but it is "Do I think this guy is worth it?" Chances are if you yourself feel that you're worth that amount, they will too.

That said, DB consultants generally make a bit more because of the fragility and messiness of what they deal with. I've done some Oracle consulting at $100/hr and that, I realize now, was a very low rate.