Why is 50% unbelievable? I have sent out newsletters for a non-profit for the last two years and their open rate is 40-60%. I assume its harder to "sell" corpo

Why is 50% unbelievable? I have sent out newsletters for a non-profit for the last two years and their open rate is 40-60%. I assume its harder to "sell" corporate newsletters but 50% doesn't sound outrageous to me.