No, I don't think it is "a rather broad statement". Regardless of the area of the country, you should never negotiate a salary as part of a group. You are "selling" your personal abilities and trying to cover your family needs. How different is the gasoline price today by regions? Are they so different? How about food products?.
I encourage you to read my article in Advance for MLP (Jan.28, 2008) where I demonstrate that all the "alleged" salary regional variations are non statistically significant and offer some advise in how to negotiate your salary.
Histonet mailing list