Because evil has its ultimate price (5)
I believe the answer is:
since
'because' is the definition.
('since' can mean 'because')
'evil has its ultimate price' is the wordplay.
I cannot quite see how this works, but
'evil' could be 'sin' (synonyms) and 'sin' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for since that I've seen before include "From that time one" , "Seeing that" , "Because; ago" , "in the past" .)