I take out everything I don't want and put in what I want. It's not about price. Editors aren't buying what you think you're selling. Like anyone else, they're buying a solution to a problem and the good feeling they get from solving the problem. So, ask questions of your customer and of others who have dealt with your customer to find out what problem you can help solve.
Pressure is mutual.
You're not the only one feeling pressure. The editor has a magazine to fill with quality material on a budget that is undoubtedly too small. A book editor has to buy enough profitable books to hang on to the job. Don't let yourself be intimidated.