2 Samuel 24:24 (KJV) And the king said unto Araunah, Nay; but I will surely buy it of thee at a price: neither will I offer burnt offerings unto the LORD my God of that which doth cost me nothing. So David bought the threshingfloor and the oxen for fifty shekels of silver.
If you serve God, it will cost you. Thankfully, the rewards far exceed the costs. If you think you are serving God but it isn’t costing you anything (not necessarily in terms of money), you probably aren’t serving God.