I just found one in my SDB, checked the priced and was amazed to find that it was worth 2mil.

Does anyone know why it's worth so much, or possibly where I got it (I did NOT buy it)?
I'm not 100% sure, but I think it's a prize from Symol hole. ._o
Check the rarity.
If it's over 101 it came from some sort of prize, such as Symol hole.
If it's somewhere between 80-100 it stocks in the shops, and the closer it is to 100 the less it stocks, so the more it'll be worth.
Either way sell it as soon as possible, before more are restocked or more are given out as prizes

Symol Hole... I think you're right. I remember winning a book there long ago, but forgetting the name... And thanks for the advice, brett.