Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
There is no limitation for a minimum or a maximum amount for Mahr. Imam al-Shafi’e narrated in his book al-Umm from Abu Yahyah that he said: 'I asked Imam Rabeeah about the minimum Mahr, he said, any amount that is agreed on by both parties. I said, ‘If it is only a Dirham?’ He said, ‘Even if it is half a Dirham.’ Then I said, ‘If it is less than that,’ he said, ‘yes, even if it is a handful wheat or a seed of wheat’.
However, there are many texts that encourage minimizing the expenditure of a marriage to make it easy and to put an end to the evil that exists because of remaining spinster or unmarried. The Prophet (Sallallahu Alaihi wa Sallam) have said: "The most blessed marriage is the one with the least expenditure".
Allah knows best.