The 128GB iPad is now on sale from Apple via the company's online store
. In the US, the Wi-Fi variant costs $799, and is currently slated to ship in 1 to 3 business days. The Wi-Fi + Cellular version is $929, and ships in 1 to 3 days for AT&T subscribers, but 3 to 5 days for either Sprint or Verizon.
In countries like Australia, Canada, France, Germany, and the UK, notably, all editions are shipping in the 1-to-3-day window. The delay on US 4G hardware is presumably linked to the need for separate CDMA units, whereas most countries only need a single GSM model to support multiple carriers.