I disagree. Contractors should never waiver on their prices. Whatever your asking price is you should always be willing to walk if your price isn't met.
For example they tend to respond to standard negotiating techniques, such as quoting them a higher standard rate then offering a discount in negotiation.
Walking away is fine as long as your confident in your ability to immediately get work at your rate but it doesn't prove your rate out - people paying it does.
There is a slightly dated, but highly relevant book I'd recommend - Janet Ruhl's Computer Consultant's Guide - http://www.amazon.com/Computer-Consultants-Guide-Strategies-...