For sure, everyone should try to get more on their offer, it can be significant. I'm still not convinced there are many secrets an ebook can unlock, vs just asking for it and trying, as always, to be both confident and likable.

But I suspect it's equally possible whether you're in a low or high CoL area, I haven't seen anything to suggest otherwise. It's unrelated to the issue of whether the company will pay you more in certain locations than others.