For its Prime members, Amazon offers the Photive SlimPad Ultra Slim Smart Cover Case for iPad Mini in five colors (Purple pictured) for $9.95 with free shipping. (Non-Prime members can spend $35 for free shipping, otherwise it's $8.22.) That's $30 off list price and the lowest total price we could find. It is able to transform into a stand and has built-in magnets to support Apple's sleep and wake feature.
BoxWave Corporation via Amazon offers the BoxWave Blackout Case for iPad Air in Black for $16.95. Coupon code "ILOVEAIR" drops it to $3.95. With $3.50 for shipping, that's $26 off list and the lowest total price we could find. This TPU shell cover features a dual matte and glossy finish.