That $399 gets a consumer the last-generation iPad (prior to the iPad Air), with 16GB of internal storage and WiFi support. You will be set back $529 for a cellular version, which is $100 less than the equivalent iPad Air models and the same as the 16GB Retina iPad mini.
The iPad 4, as you might expect, is significantly improved over the iPad 2. The newer version not only includes a includes Apple’s custom dual-core A6X processor, a 5 MP iSight camera, and 1.2 MP FaceTime camera. It is only available in the 16GB storage tier.
With this move, the last iPad with the older 30 pin connector is now gone. This could mean that Apple will soon eliminate the iPhone 4S, especially since it has just introduced an 8GB iPhone 5c; the 4S is the last current iDevice with the 30 pin connector.