Gun shop price war may show value of money (10,5)

I believe the answer is:

purchasing power

'value of money' is the definition.
(measure of a currency's value)

'gun shop price war may show' is the wordplay.
'may show' indicates anagramming the letters.
'gun'+'shop'+'price'+'war'='gunshoppricewar'
'gunshoppricewar' with letters rearranged gives 'PURCHASING POWER'.

I've seen this clue in The Guardian.

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