In this question no need to do any computation if and only if we carefully observe the prices of the 4 commodities.
Process of elimination :P
Arhar- The lowest pice of Arhar is greater than or Equal to that of Sugar.
Pepper- The lowest price of Pepper is much much greater than Arhar.
Gold(obviously costly :P )- The lowest price of Gold is Greater than that of Arhar.
Sugar- The highest Price of Sugar is less equal to the lowest price of Arhar.
But, on an Average the Sugar price is seemingly less than that of Arhar.
Hence, (C.) Sugar is the answer.