Conservation is related to Law. Law is related to Implication. Implication is a type of Accusation. Allegation is a type of Accusation. 
Tax is related to Revenue. Revenue is the opposite of Cost. 
Conservation <--RelatedTo--> Law <--RelatedTo--> Implication --IsA--> Accusation <--IsA-- Allegation 
Tax <--RelatedTo--> Revenue <--Antonym--> Cost 