The Prophet of Allah, sallallaahu ‘alayhi wa sallam, did not exaggerate in the dowry of his daughters:

The Prophet of Allah, sallallaahu ‘alayhi wa sallam, married his daughter with a very small dowry. Ibn ‘Abbaas (a Companion) narrated that ‘Ali said: “I married Faatimah and the Prophet of Allah, sallallaahu ‘alayhi wa sallam, said: ‘Give her something.’ I said: ‘I have nothing.’ So the Prophet of Allah, sallallaahu ‘alayhi wa sallam, said: ‘Where is your “Hutami” armor?’ I said: ‘It is with me.’ So he told me to give it to her.”

Ibn Al-Atheer (a scholar) said: “Hutami armor is in reference to a tribe called Hutamah ibn Muhaarib that produced it. Or, it is a  reference to the word’s original meaning in Arabic of breaking, i.e. it breaks swords when they hit it.”

This simple armor was the dowry of the daughter of the Messenger of Allah, sallallaahu ‘alayhi wa sallam, his youngest daughter, and the leader of the women in Paradise!

As for the modern custom of making the dowry very expensive, this is not from the guidance of the Prophet of Allah, sallallaahu ‘alayhi wa sallam. If making the dowry a large amount was a form of honor (for the bride), then the Prophet of Allah, sallallaahu ‘alayhi wa sallam, would have been the first to do so.