When King David purposed to thankfully worship God for holding back His hand from more extensive punishment on the people of Israel, it was proposed to him that he make offerings on the rocky threshing floor of Araunah the Jebusite.
David the King might have appropriated it by eminent domain, for the benefit of all Israel.  But he knew he had been the cause of the Lord’s anger and felt a conscience against confiscating this land for a place of worship.  When Araunah offered to give it to the King, David answered,

No, I insist on paying you for it. I will not sacrifice to the Lord my God burnt offerings that cost me nothing.            2 Samuel 24:24

Our own worship may cost us something, too.  The cost might be setting the alarm clock in order to get up in time to attend church on the only day you have to relax.  It may be turning off the TV in order to get down on the floor and play princess with your daughter.  For a friend, it meant getting rid of the computer and cell phone so he would have fewer temptations to seek out pornography.  For one who is fasting to strengthen her concentration in praying for something important to her, her sacrifice may be willingness to be hungry for a time.
The week before Jesus was crucified, his friend Mary of Bethany exercised costly worship, anointing His head with very costly ointment perfume, “preparing Me for burial,” Jesus said.  When onlookers criticized her for “wasting” the precious perfume, He said,

Truly I tell you, wherever this gospel is preached throughout the world, what she has done will also be told, in memory of her.       Matthew 26:13

Are there things in our lives we should sacrifice, for the sake of being all that God wants us to be?  For the sake of worship?  Costly worship is very sweet-smelling to God.