It probably contains a lot of gifts given, many by family. That’s the kind of thing every family wants to pass down.
I should have elaborated that the crap jewelry is there for occasions when they don't want to let go of the good stuff. Kate gets the good stuff, Meghan gets the crap that's there for just such occasions.
“It probably contains a lot of gifts given,”
Google Images “royal jewels”. Very interesting. Inheritances. Multiple loose gems gifted by heads of state later made in to tiaras, necklaces, brooches. Simple purchases. Original owners and the jewelers who created them.