We have no idea who purchased the jewels. Was it Máxima? The Prince? Was it a gift by someone in the royal family?
The one member of the royal family purchases a Porsche 911 (the late Prince Friso) and the other member purchases lands in Argentina, Mozambique and Greece (Willem-Alexander) and again someone else purchases jewels (there are more new additions than this tutti frutti set). So what is waste of money? It depends very much on the person and how deep the pockets are.