I just can't stress this enough. Don't negotiate yourself into a corner. If you tell a man you can't marry him unless he buys a minivan, you might have to find a new fiancee if he calls your bluff. Don't negotiate for the sake of negotiating. Don't tell a woman you can't stand the China pattern just because you feel obligated to have an opinion.
Companies present what they think are fair compensation packages when they make an offer.
If you think their research may have been lacking some current market data, you should share this data with them, but you don't want the cost of good will lost to be higher than the potential for cash gained. Don't negotiate based on your financial need. Bill Gates isn't going to marry you just because you've decided that's the lifestyle you want. You are paid based on the current market value of the total skills package you bring to a company and your ability to positively affect the company's overall bottom line. Do have your data together when you enter into negotiations.