“a year’s wages” (NIV) = 300 denarion. A denarius was the principal silver coin of the Roman empire and was worth about a day’s wage (Mt 20:2), so, allowing for the Sabbaths, this would be worth about a year’s wages. Three hundred denarion was not an excessive price for such a valuable perfume which would have been worth much more in Rome. In contrast, note that it would have taken less to feed 5,000 men and their families (Mark 6:37). The point is that this alabaster of nard was extremely valuable.

Matthew 20:2  He agreed to pay them a denarius for the day and sent them into his vineyard.

Mark 6:37  But he answered, “You give them something to eat.” They said to him, “That would take eight months of a man’s wages! Are we to go and spend that much on bread and give it to them to eat?”

Jewish women were very fond of perfumes and Mary probably had this nard from the time before she started following Christ.

Baptism was used by the Jews to admit Gentile converts. The males were circumcised but both males and females were baptized, denoting the ceremonial removable of the contaminants they had acquired in the Gentile world. However baptism of Jews was unheard of.  Gentiles needed cleansing, of course, but Jews were God’s people and to put them into the same class as Gentiles would have been horrifying.  However, some people thought that baptism would come with the advent of the Messiah. Eze 36:25, Zech 13:1

Ezekiel 36:25  I will sprinkle clean water on you, and you will be clean; I will cleanse you from all your impurities and from all your idols.

Zechariah 13:1  “On that day a fountain will be opened to the house of David and the inhabitants of Jerusalem, to cleanse them from sin and impurity.