Expercom offers the refurbished Unlocked Apple iPad Air 16GB WiFi + 4G LTE Cellular Tablet in Space Gray, model no. MF020LL/A, for $299 plus $6.50 for shipping. (A Sprint SIM card is also included.) That's a buck below our mention of a new locked unit from three weeks ago and $174 under the lowest total price we could find for a new locked unit today.
Note: It includes a Sprint SIM card, but this iPad is SIM unlocked and can be used with your LTE carrier of choice. A 90-day warranty is included.