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.
To provide an anecdote the other way: I do small business software and webhosting in the southeastern US, and I have often had prospective clients seem taken aback when I mention my rates, which are nowhere near the rates being bandied about in this thread. If you choose to sell your services to small businesses, be prepared to fit into a reality where the client thinks $80 an hour is a terribly high amount for a 5-10 hour job, and is prepared to just not have the work done instead. Very little is actually required for most small businesses; some of them are still considering upgrading the old machine running Win98 that's been doing invoices for 10 years, and unless it breaks, it's "good enough".
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.