'Ointment' in the Bible

(It was that Mary which anointed the Lord with ointment, and wiped his feet with her hair, whose brother Lazarus was sick.)

Then took Mary a pound of ointment of spikenard, very costly, and anointed the feet of Jesus, and wiped his feet with her hair: and the house was filled with the odour of the ointment.

Why was not this ointment sold for three hundred pence, and given to the poor?