My Perverse Equivalent Exchange System In Doomsday

My Perverse Equivalent Exchange System In Doomsday,

One cannot gain anything without first giving something in return. To obtain, something of equal value must be paid.

The life saving system that Long Yu received supposedly follows this rule. Unfortunately, the price required some times can turn out to be somewhat strange.

'System, I want to exchange for something that can regrow an arm.'

Searching....
Recommended option:
Limb regeneration capsule
Price required- 20kg of mutant lizard fertile s.e.m.e.n