[Illusion]

"But then why aren't older items inflating as much as the current ones?"

.....
Just sit that in your head for a minute....
It will come to you....

That's sorta like saying why isn't that one 2004 MC on Gaia isn't worth over 10 million gold then its current million price tag.
So..
Is the item popular?
Items tend to sell more when they are just released, and increase/decrease by popularity.

Theres 2 other reasons I can post but I want you to figure them out on your own here.