Very Common - Blue Backed Cards = 100-300 NP
Common - Red Backed Cards = 300 - 500 NP
Uncommon - Pink Backed Cards = 500 - 1000 NP
Quite Rare - Green Backed Cards = 1000 - 2000 NP
Rare - Purple Backed Cards = 2000 - 5000 NP
Very Rare - Black Backed Cards = 10 000 - 20 000 NP
Amazingly Rare - Gold Backed Cards = 30 000 - 50 000 NP
Out Of Print - Holographic Backed Cards = 100 000 - ........
I hope this Helps you find the rarity and value of you collection Have Fun !!!
All Prices are based on Neopets Ranges on card value.... But you know how inflation works ......