Why Does Perfect Amethyst Worth More Than Other Gems?

I'm new to the website, and I did my first trade, I was interested in Jade Talons and saw that the majority of people wanted 5 Perfect Amethyst or 10 Perfect Gems to trade.
This tells me that Perfect Amethyst is worth the same or more than 2 of any other Perfect Gem, but why is that?

i think it is because they are used for Caster Amulet crafting

More cube recipes need Perfect Amethyst. Just hover your mouse on any " Perfect Amethyst" on this page and you will see.

generally, in game, you can sell 10 perfect amethysts for 1 Ist, also rubies(about 20 for Ist, and pskulls(don't know how many for Ist) but the rest, in normal trades, about 35 for Ist(most people just sell the ammyes separately and the rest 35 for Ist atm) however if you gather skulls rubies and ammies separately you can get more then 1 Ist for 35 pgems

different pgems are used in crafting receipes, and the rest are very usefull for rerolling high ilevel charms in the hopes of getting a high value skiller(in cube any 3 pgems+ charm rerolls it, so if you reroll a grand charm that is dropped from Baal nilathak or Baal, or a Terror zone in a game created by a char that's at least level 90(gives the dropped charm ilevel 91), you have the chance to roll a +45 life skiller which is worth very very much)

save those gem shrines for flawless ones