This article is from the Paper Money Collecting FAQ, by Bruce Giese firstname.lastname@example.org with numerous contributions by others.
When I first started collecting paper money, I had a Chinese note
which I couldn't identify, so I asked a colleague who was from Taiwan.
Figuring "Hell" was probably some obscure province in China I asked
him where the note came from. After he stopped laughing, he explained
to me that a Buddhist tradition is to create paper money which is
supposedly legal tender in the Hell afterlife. This paper is then
burned so that dead ancestors who might have ended up in Hell would
have something to spend. Some people even create paper cars, houses,
etc. and burn them so their ancestors can have basic luxuries. Noting
that the denomination on the note was one million, my colleague figured
there must be severe inflation in Hell.
How much are these notes worth? Face value. :-)
Some people collect various forms of hell money.