6. Madonna and Guy Ritchie - 2000

Estimated Cost: $1.5 million

Their marriage didn't last, but their wedding ws one for the books. The singer and director said "I do" at Scotland’s Skibo Castle, where she wore a diamond tiara once worn by Princess Grace of Monaco and he (and baby Rocco) wore a kilt. The guests, which included Gwyneth Paltrow and Sting, then partied in a "basement" that was converted into a dance club.