Just divide the cost (total cost) by quantity;

example if you have 1 pack of candy( 20 pcs.) a cost of 1 pack is P50.00;

20pcs( cost of a pack)/P50.00 =0.4 cents each..

this time,you have  to add the expenses incurred upon purchasing and 
regular marked up, to come up a proper profit (net)...

i;m sory the figure must be in reciprocal..50/20=2.5P each...