Cheap is the opposite of Steep. Steep is related to Climb. Climb is related to Struggle. 
Subject is related to Reply. Reply is the opposite of Ignore. Ignore is the opposite of Stare. 
Cheap <--Antonym--> Steep <--RelatedTo--> Climb <--RelatedTo--> Struggle 
Subject <--RelatedTo--> Reply <--Antonym--> Ignore <--Antonym--> Stare 