It depends on the info that's being exchanged. if you are paying that much for someone to just tell you: let your first meal be this many grams protein, this many grams of carbs, and this many grams of fat... eat whatever your body feels comfortable ... blah blah blah and that kind of stuff without specific details about anything... yes, he's just ripping you off and taking advantage of his clients. for $4000, i see that he should be cooking the food for you
... you can hire a chef for 1/4 of that amount.
If he tells you everything down to the smallest detail (the type of food, the amount, what time, what kind of training, reps, sets, exercises, supplements, super supps, when to take them, unlimited phone calls... etc) then it would seem to be a fair price depending on the competitor.
I would rather pay $2000 on GH than pay $2000 on a prep guy who will just tell me shit i already know (which happened a while back).