I know they have quite a few pieces in various stones, but not tiaras or full sets. That is why I'd like them to invest in pieces. Considering that most of the stones listed are not that expensive and the King spent a million on a new speedboat I think the family has the resources to buy some interesting pieces.
I personally would have loved it if they had spent the million on the Faberge aquamarine tiara of the Grand Duchess of Mecklenburg-Schwerin (married to a first cousin of Queen Juliana).