I seriously doubt this is true. A Spanish newspaper reported last month that the King was negotiating but one family member did not want to sell. But that article was very suspect and shoddy. In any event, I don't think the King has 7 million euros to spend, and certainly wouldn't do so publicly in this economy and in the face of the recent negative press regarding the elephant and his son in law's investigation.
As to the speculated price, that parure, even though the tiara was redesigned by Bulgari and the necklace is by Cartier, is worth at most half a million, double that for its historical/royal provenance...so a max of $1 million (dollars not euros...and that is the high high end). By way of comparison, the Paley aquamarine parure by Cartier sold for the following: Tiara $512,000; Necklace $392,000