Is it seriously not possible to buy a factory unlocked cellular iPad in the US for full device price?
Past history has shown that at least in the US, all iPad models, regardless of carrier designation on the box, are in fact unlocked. The only thing that makes a T-Mobile iPad a T-Mobile iPad, is that a T-Mobile SIM just happens to be inserted in the slot when you buy it. Same for AT&T and Verizon.
The only caveat is that if you buy from Sprint, those
MIGHT be locked given Sprint's really restrictive policies. And buying an iPad from a GSM carrier
MIGHT mean that there's no CDMA enabled. Time will tell on this though, once people get their hands on them and start swapping SIMs around.
Also, if you're buying from the Apple store at least, then you ARE buying at full device price. There are no contracts offered for iPads. This might be different though if you buy from the carrier itself.
If you want to be absolutely sure you have an unlocked iPad, get a Verizon model. Per the deal they made with the FCC for LTE spectrum, all their LTE devices have to be unlocked.
One last thing: it looks like according to
Apple's LTE page for iPads, there's only one iPad Air model number for basically, all carriers everywhere. So this hopefully means that they crammed all the electronics they ended to cover all the bands and networks into a single model this time around.