I have a small, but profitable consulting company working for clients across Europe and the US. If there's one thing I've learned, it's that if some of the first words out of the client's "how much do you charge?", it's an awful contract. They're focusing on cost, not value.
I don't charge as much as top-tier consulting firms, but I do charge more than most freelancers. Clients generally know who I am by reputation or referrals and they're happy with my work. For clients who want to nickel-and-dime the contract, it's miserable.
Still, my favorite was one client who wanted to pay me far less than what I ask and demanded a fixed bid on a small, two-week contract. I agreed and got finished in three days. He wound up paying a lot more for my work than if he had agreed to my rate up front. I charge more, I get done faster. And that's with documentation and tests.
So yeah, don't undercut yourself by charging too little and don't hurt yourself by accepting contracts with those who don't appreciate your value. It's all grief in the end. I walked away from one year-long contract which offered a reasonable rate, but still less than what I charge. To this day I still don't regret that decision, though many would have compromised. My very next contract was my normal rate on a rolling contract. It's been less than a year, but I've already earned more than I would have with the year-long contract and the company is very happy with my work.
(Plus, I used to sell cars and when you sell cars, you quickly learn that the happiest customers are the ones who pay the most)