They've made an offer. There is the possibility of a deal with these guys - the job looks healthy, the money close. You don't want to haggle.
Therefore ...
If the offer is acceptable, accept it and get on with life. If not, simply refuse: "I'd love to join you, but I can't accept this offer. Thank you very much."
Or you could refuse their offer by default, and then accept the offer if you like it. This distinction is important because the seller is less likely to use unfair pressure tactics if he can only make one offer. An example of this would be the car faxathon example I cited in DontHaggleJustWalk. -- StephanBranczyk
They want you. They have to ask why. Then you name your one issue: "We're not even close on the money." Or whatever. Consider NeverStateYourNumber.
Offered for your approval - rj
If the going in assumption is that you reject negotiation ("You don't want to haggle"), then I guess that leaves you with AcceptOrRefuse. You could also rule out refusal and leave accept as your only option. If something is important to you now, you should probably address it now. If it is truly important, the issue will continue to irritate you and lead to problems in the future. Also note that the issue does not need to be solved now. Often times items that are not initially negotiable become negotiable after you have worked together and become known quantities to each other.
Part of the NegotiatingPatternLanguage.