For mega power mons, those don’t really have much demand, I think
10k per mon shd be a fair price, but it may go lower, depending how
many people hunt it.
At Market Insider, it shows 50k PD, but it is not accurate at all because as
you can see the range line, which is stagnant continuously at the
same price for 3 years, which means no more Santa Birbs were sold
during this time, so Santa Birb's price would be more.
At Event shop, It costs 6,500 EP which equals to 650 Nuggets
including its egg dex, so it would cost below half the price of it,
i.e., about below 350k-400k PD.
^^
Caterpie has Rarity Easy, so open the Spoiler Pokemon, scroll down
to Shiny and look on the Rarity. There is no difference between
male and female, cause Caterpie is 50/50 and there is no SM
Caterpie, if you mean Shiny Giga Butterfree, than it´s regulare
shiny Butterfree+Dynamaxcrytals, but they don´t have a fix price.