@NSK
You might be in luck of finding a rare one, but usually, it affects the value negatively.
Concerning really common stamps like this German one, a perfin will always have a positive effect on the value. And even rare issues go higher in auctions than the non-perfinned ones.
Just as an example ... one pretty low price Finland stamp was sold on
ebay for over 300 USD, because it had a W perfin in it.