i don’t know exactly how your groups are configured (there can be all sorts of variations),
but off the top of my head something like this would probably work:
a) you will have to put all ingredients that have the same price into their own custom groups.
b) depending on how many ingredients end up being preselected in each group, set:
“ingredients free (of this group; cheapest first) ” to that number of preselected ingredients
i would think this would work but feel free to also send me a screenshot of all/any custom groups you have set up for this particular item together with a screenshot of the list of ingredients available for this (just to know how the prices are set up there)