If they're dumb enough to make that request, I bet they're dumb enough to be swindled themselves. I think you could have a lot of fun with that conversation, if you're quick with your wit. It might even be profitable, if they'll stupidly agree to something silly in a legally binding manner.
Like: "Hmmm... I dunno... Well, okay. I'll charge you $5,000 to for my consultation on assembling the list. But I have to charge you a fee for each subsequent amendment to list. Once you've paid for my consultation on the list, then we can talk about the actual cost of the work itself, and whether you want to pay me to actually do anything."
On the one hand, you have a point, and it's really tempting to give into this sort of ethos, as an approach to diet and nutrition, but at some point it becomes important to acknowledge that a very real and practical biology reigns over your internal organic processes. These processes can be measured and understood at a chemical level.
We don't understand them perfectly, and many people (maybe more than half the world?) don't actually measure out their hunger in grams and milliliters, or understand the fundamental building blocks of metabolism at the chemical level, and get buy just fine, purely trusting their guts.
One size doesn't fit all, and sometimes cravings are correct, but not all the time. Addictive substances and microbes show us that "what you want" isn't always "what you need."
Opiates have been around for centuries, and demonstrate that just because you might feel a hunger for something and find it satisfying doesn't mean it's good for you. You're body's understanding of the world around it can be distorted. Sometimes the things that distort it's intuition are odorless and colorless. Natural food does not come with labels (and even labels can be wrong), and if you're uncertain of the purity of the water you boil your meat in, well, maybe there could be something in it that is sapping and impurifying your precious bodily fluids.
Meanwhile, it might be counter-intuitive that bread mold can ward off infection, but then again we have penicillin which has proven to be a powerful and valuable anti-biotic.
So, feel free to operate on faith and emotion, but going through life with your blinders on, you might be caught off guard by things that you could have avoided if you hadn't chosen to ignore them.