A rough estimate for now would be around 500-600 USD for a complete head with all shown parts.
The head can not be worn, it is for display only.
To make them wearable as they were made for the movie would take too much effort.
The original heads had one inner shell and an outer skin for the background characters and two inner shells and one outer skin for the hero characters.
After i built up a complete "Kounan" character mangalore bust form the Fifith Element i was asked if i want to sell it. https://www.therpf.com/forums/threads/fifth-element-mangalore-mask-restoration-no-3-kounan.302485/ I like my bust and i want to keep it in my collection but i am able to make...