The 16GB iPad Air 2 from T-Mobile is zero dollars down with 24 monthly payments of $26.24, for a total of $629.76. There is also a $10 SIM Starter Kit required making the full total $639.76. T-Mobile currently does not have the 64GB or 128GB models listed for pre-order, but you can pre-register here.
The 64GB iPad Air 2 model is normally $729 and the 128GB model is $829. So T-Mobile customers should expect to pay $30.37 a month for 24 months for the 64GB model, and $34.54 a month for the 128GB model.