There is an English expression: ‘There's no such thing as a free lunch’.  It means that you can never get something for nothing ... if somebody gives to you it is only because they want something back.  While that is a common human idea, it totally excludes the grace of Christ.  Jesus was addressing people who were invited to a feast (Luke 14:1) - they were expected to invite their host back or to give him a gift of some kind.  But the Jesus-way of living and loving is different.  Jesus said do not invite people who will invite you back, don't give to those who will return the favour.  Stop playing social games and give because there is need, and no possibility of recompense in this life.
 
It has been jokingly said that the rewards of Christian devotion and service are, ‘out of this world’.  And that is literally true. No act of kindness goes unnoticed by Jesus.  No sacrificial generosity will leave you eternally impoverished (Luke 18:29-30).  The pay-back is from God Himself - not those whom you have helped - and it comes when Jesus returns and the dead in Christ are raised first.  As Hebrews 6:10 says, "God is not unjust; he will not forget your work and the love you have shown him as you have helped his people and continue to help them."

James, the half-brother of Jesus, reminded the church that such Pharisaic behaviour is always at risk of invading the church (James 5:1-6).  An overdependence on money, social pride and self-indulgence is not the Jesus-way.  Treating workers badly, taking bribes and being dishonest aroused God’s anger in the Old Testament (Amos 5:11-12), and still will.
 
God has a very long and accurate memory.  He remembers those who have already received their reward from human beings and discounts their service as self-seeking (Matthew 6:1-4).  However, He also remembers the sacrifice of those who give until it hurts, and beyond.  That is not speaking of those who have been manipulated into giving money or services; but of those who have freely chosen to serve their Lord by meeting the need of people who cannot help themselves.  That was exactly what Jesus did when He died on the cross - securing salvation for those who could not save themselves.  All those who are grateful for what Christ has done should want to show it in much smaller ways as they serve others.  Those who refuse to serve or give sacrificially may well have little gratitude for God’s grace to them.