Rate
Rates for agri products fluctuate a lot depending on various conditions, quality of the product, supply vs demand, season etc.
The Coconut you are referring here is, is it tender coconet or dry coconut ? @ Rs 4/ for tender coconut is quite reasonable and for dry coconut it is very high offer.
Coming to Chikku, 20 K price, we can not say is it reasonable unless we get to know the age of the trees, period for which the crop is sold, yield quantity.
Pl do let me look at pictures of the chikku trees with crop so that i can guide you if the offered price is reasonable - Ramki