Regalia which are never intended to be worn are usually not that expensive. The Spanish and the Dutch monarchy both have relatively cheap regalia made of gilded silver without precious gems.
The Belgian, Luxembourg and Monegasque monarchies do not even have any regalia at all.
I think the Bandjermasin Diamond mounted into the Dutch regalia was a) an insult to Indonesia and b) a waste of the precious stone.
Pic: part of the 1848 State Regalia on a table
A footman holds the wrong sceptre (Regalia 1815) with the Crown, Orb and Sword-of-State of the Regalia 1848