a quick google search yielded the answer:
The world's most expensive wedding was thrown by Lakshmi Mittal for his daughter Vanisha Mittal and and her fiancée Amit Bhatia on June 22 2004.
The wedding was held at Vaux le Vicomte a 17th-century French chateau on the final day of a 6 day celebration.
The estimated reported cost of the wedding celebration came in at a mere $60 million USD.
Lakshmi Mittal also holds the record for owning the world's most espensive house.


what made it so expensive???
Mittal family had sent out 20-page invitations in silver boxes, while 1,000 guests were flown in from across the world and put up in a five-star Paris hotel.
The five-day festivities spread across some of France's most famous settings, including the chateau built for Nicolas Fouquet, King Louis XIV's finance minister.
One night there was a party at Versailles while another event reportedly took place at a wooden castle temporarily erected in Parc de Saint-Cloud, Forbes reported.
Pop signer Kylie Minogue performed at the event, while 5,000 bottles of Mouton Rothschild were emptied with wine tab estimated at $ 1.5 million. Ladies were said to have sported special henna decorations and received luxe goody bags of
jewels.