1. $200 for the TX1 is a much lower entry point for GPUs than $600 for the TX2
2. According to Nvidia (see comparison here: https://devblogs.nvidia.com/parallelforall/jetson-tx2-delive...), the TX2 is about twice the performance of the TX1, but since the cost of the TX2 is about 3 times the cost of the TX1, I think you get more "bangs for your bucks" with this offer