For those times you work hard finding the product that will suit your customer's needs only to face getting beat up on the price, here are a few helpful ideas to preserve your margins:
Establish a consistent position. Consider the automobile industry. During '60s, '70s, and '80s, negotiating prices was so common that nobody would dream of paying the sticker price. Then came Saturn. Saturn dealers said, "This is our price." It changed the way America buys cars.
Understand what customers want and need. Determine if they simply don't see enough value in your offer to justify the price, or if they're just testing to see if you've "padded" the price. If it's the former, then you need to keep selling and build more value. If they're just testing, then hold your ground.
Recognize special circumstances. Sometimes it's OK to discount - if the customer is buying a large quantity or is a potential source of much more business. But set guidelines for discounting.
Never lower the price. At least, not without getting something in return. If you must negotiate, take something away every time to lower the price: "I can take the price down a bit - if we don't include a DVD player. How about an AM/FM radio instead?"
Remember that you represent your employer. It's not your money to give away. Your job is not to represent the customer in negotiations, but to present your employer.