John 12:4-5

Judas, as well as some other disciples who were present (Matthew 26:8; Mark 14:4), objected to what seemed to be an extravagant waste. Three hundred denarii was a full year’s wages for a working man in that culture. Mary would not give to the Lord what cost her nothing (cf. 2 Samuel 24:24). Real worship always costs the worshipper; it always involves a sacrifice.

"When she came to the feet of Jesus, Mary took the place of a slave. When she undid her hair (something Jewish women did not do in public), she humbled herself and laid her glory at His feet (see 1 Corinthians 11:15). Of course, she was misunderstood and criticized; but that is what usually happens when somebody gives his or her best to the Lord." [Note: Wiersbe, 1:339.]