how much value do gold stars lose upon damage?

[zaeden906]

So, I was wondering how much potential value does a gold star lose with damage? such as
slight-heavily creased?
whitening
etc...

 

[PokePop]

creasing: they lose most of their value.

 

[flygon_frank_66]

Anything past the normal production wear usually decreases the value by 50% or more.

That's just the standard I use for my cards.