Part of the treasure in heaven that Jesus talks about is the feeling of purpose and satisfaction a person has when they know they are performing the will of God. Those who put themselves and money first often complain about life feeling empty and meaningless. Jesus pays those who serve him with meaning and spiritual abundance in their lives and hearts instead of money.

Praise be to God; whose compassion is all-embracing and Whose mercy is universal; Who rewards His servants for their remembrance [dhikr] [of Him] with His remembrance [of them] - verily God (Exalted is He!) has said, 'Remember Me, and I will remember you' - Opening lines from Kitab al-Adhkar wa'l Da'awat of the Ihya ulum ad-Din