Groupon offers the refurbished Apple iPad with Retina Display 32GB WiFi Tablet in Black, model no. MD511LL/A, or White, model no. MD514LL/A for $519.99 with free shipping. That's $29 under our March refurb mention and the second-lowest total price we've seen for these models. (We saw a refurb for $20 less in March.) It's also $40 below the cost of a new unit with pickup elsewhere. It's 9.4mm thick, weighs 1.4 lbs. and features a 9.7" 2048x1536 Retina display, A6X dual-core processor with quad-core graphics, 5-megapixel iSight camera with 1080p video recording, 1.2-megapixel HD FaceTime camera, voice dictation, 802.11n wireless, Bluetooth 4.0, Lightning connector, up to 10 hours of battery life, and iOS 6. Deal ends May 27 at 12:59 am ET.

A 90-day warranty applies, although it's unclear who supports it.