With the introduction of the 9.7-inch iPad Pro today, Apple has cut the price of the iPad Air 2 by $100. (The "2" is probably the end of the Air line-up; I expect iPads will now only be offered with "pro" and "mini" monikers.)
The entry-level 16-gigabyte Wi-Fi model now costs $399 and the 64GB model is $499. Cellular-equipped models with these amounts of storage are now $529 and $629, respectively. And the 128GB option has vanished from the line-up.