What it costs to produce an attractive-looking coin? (6,5)
I believe the answer is:
pretty penny
'what it costs to' is the definition.
I know nothing about this answer so I cannot judge whether this works.
'an attractive-looking coin?' is the wordplay.
'an attractive' becomes 'pretty' (pretty can mean good-looking or attractive).
'looking coin?' becomes 'penny' (penny is a kind of coin. I am not sure about the 'looking' bit.).
'pretty'+'penny'='PRETTY PENNY'
'produce' is the link.
Can you help me to learn more?
(Other definitions for pretty penny that I've seen before include "Large sum of money" , "Large amount (of cost)" , "A tidy sum of money" .)