An important difference: Tesla can produce all their own batteries, and none of the competitors are even close to Tesla's production levels. So Tesla gets better batteries for cheaper.
Panasonic makes the battery cells. Tesla builds them into the battery pack that goes into the final products. And this happens under the same roof, and the cell design is a joint venture. Tesla's battery cell manufacturing far from a black-box process where Tesla wrote a check and a third party delivers battery cells with no other involvement.