Ebay and ATT

My husband and I upgraded our phone to iPhones.  We were able to take advantage of the new deal where we got 2 phones for $49 each and a $15 data plan.  We have wireless internet at home so we are able to use the cheapest data plan since we won't use our data plan up while at home.  And then I noticed the Otterboxes that protect the phone at the store were $30.  I knew I could get them cheaper so I've been on ebay and got one case for $8.50 and another for $11 with shipping.  My ATT receipt said I saved over $800 (I guess because their price on the phones are $499.)  But we have the 3G phone and I know they are pushing them out to make way for the iphone 4.  Either way - I feel like I saved money today and I'm always happy about that.