Grabs a bargain when pictures get more expensive (5,2)

I believe the answer is:

snaps up

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'grabs a bargain' is the definition.
(I've seen this in another clue)

'pictures get more expensive' is the wordplay.
'pictures' becomes 'snaps' (I can't explain this - if you can you should give a lot more credence to this answer).
'get' means one lot of letters go next to another.
'more expensive' becomes 'up' (I've seen this in other clues).
'snaps'+'up'='SNAPS UP'

'when' acts as a link.

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I've seen this clue in the Evening Standard.

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