Opportunity Cost according to BusinessDictionary.com is a benefit, profit or value of something that must be given up to  acquire or achieve something else.

The bible counsels us to not give the devil an opportunity (Ephesians 4:27), which in layman’s terms is “If you give the devil a ride,  he will end up driving.”
The opportunity cost of giving the devil an opportunity is extremely high.

Giving the devil an opportunity in our lives will make our lives have no opportunity for the Holy Spirit of God to work in our lives, for God is light (1 John 1:5) and light cannot co-dwell with darkness. It is one or the other.
We must first submit to God so that his light fills our life and subsequently resist the devil who and he will flee from us (James 4:7).

Points to ponder:
Who is driving your life? Who is driving my life?

Ephesians 4:27 (ESV)
27 and give no opportunity to the devil.