How much are people paying for "negotiation consultation?" The ideas of leverage and negotiation are not all that hard to understand
She charges $500 for 7 days of consultation via email or chat. I got a total of maybe 4-5 emails from her, and didn't feel it was helpful. That said, I wanted to have the support of someone with more of a track record with negotiation because of a spousal hire issue I was facing, and particularly wanted feedback in how hard to push/how to phrase communications around the spousal hire issue. I didn't seek her out (or really use her for) any more general support in terms of asking for start-up, salary, other kinds of negotiation issues that I view as more straightforward.
I would say, for $500, the negotiation service might be worthwhile IF you are someone who really struggles to be assertive about your needs, who doesn't have a lot of support from mentors/letter writers around negotiations, etc.
I also think, re: earlier comments above about getting feedback from mentors and letter writers - between myself, my spouse, and many friends who applied this year, the advice we got varied wildly across mentors, in part based on their own personalities and where they were/had been working. Of course, we'd all love to have super supportive mentors who have their pulse on the job market and are able to give you useful support, but some folks don't - either their advisors have been off the market for so long that they don't know what's realistic anymore, or they haven't trained other mentees who went the academic route, or their career isn't in the type of career you're looking for (for instance, if you have a letter writer who's always been at an AMC but doesn't know about arts and sciences jobs).
Anyway, I wouldn't say she's a godsend, nor would I say her services are a total waste of money - it really depends on what you need help with, what your other resources are, etc.