I am saying know your customer base (like any business)
If you don't you are guessing - as i said my experience is motorbike rallys since 1993 (basically a bunch of bikers turn up friday night pitch tents, spend sat & sunday nights drinking in a bar with a bunch of stalls around an arena outside, a stage with bands on both nights and usually a ride out and custom show on the saturday afternoon). look at
https://mapevents.co.uk/into-the-valley/
I also go to a local covers band "festival" locally each year which is bars, stalls & stage with camping.
The products on the stalls and the pricing/variety of food/drink available are chalk and cheese.
Bike Rally, couple of vans doing fried&chips plus something else (pizza or noodles or curry), stalls selling belts, buckles, bike clothing, jewelry, tankards and camping essentials. Beer large choice of real ales and c £3.50 a pint
Festival, loads of food vans selling all sorts of random things (like churros stall) at high prices, stalls selling hats, glowsticks, mosquito flares, face painting, random tat, tshirts, hoodies, vuvuzalas, fancy coffee and bubble tea. Beer, 1 or 2 ales, couple of largers and a fizzy cider at c£6-7 a pint