WWE were the ones who said that is the number needed for them to be in the break even area considering the millions spent for the Network's launch ($50 million range). That goes on top of the monthly costs which includes paying MLB for the Network's tech.
Has to be a consistent 1.4-1.5 million paid and not just because they hit it once means they never need to hit it again to break even.
2 million gives them a nice profit while the plan for 3-4 million would help cover other areas of the company losing money or not performing well. Once again those have to be consistent in order for the WWE to get real benefits.