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Bought my iPad air 2 at the Apple Store, signed up to add it my mobile share plan, got 100 credit for 2yr contract.
 
From what I understand you can get this discount no matter where you bought it if you bring it into an AT&T store to add it to a 2 year contract plan. If you do it after the fact it is a bill credit.

That's what I did with the Mini 2 that we already owned, got a 2yr contract and it effectively brings the monthly bill down to $5.833333333 I believe.
 
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