One thing that really maddened me when I was in sales was seeing how every company I worked for gave problem customers preferential treatment. They lived up to the saying, "The squeaky wheel gets the grease."
Not in my house. My company gets calls all day long from people who want extra guarantees, names and numbers of references, previews of my book, etc etc before they buy. Instead of catering to these people, my customer service reps are instructed to say, "I'm sorry, but we cannot provide that. If you feel that way then don't buy it." Why? Because I would lose money having my staff spend time on these people.
When I sold telephone systems there were those customers who paid full price and those who drove hard bargains and wound up negotiating the price very low. Guess what - the customers who paid full price had my full attention whenever they needed help. I was always happy to drive out to their offices to assist them. Those who got deep discounts were simply told to call the 800 number. Not my job, sorry.
You get what you pay for in this world. My favorite business author, Robert Kiyosaki, points out that those who drive hard bargains and negotiate favorable discounts usually aren't smart businesspeople at all. They're just plain cheap. The excellent business book "The 48 Laws Of Power" points out that it is wise to pay full price because in addition to the product itself it buys you the respect and full assistance of those who sold to you.
The bottom line here is not to waste your time on "squeaky wheels" who demand more of your time and attention than they deserve. Save that for your paying customers. If you spend endless amounts of time on a hardcore negotiator, just remember that while you're arguing with this prospect over price, your competitors are out selling to the good prospects you really want!