By way of follow up, I thought that 50,000 USD figure sounded very low. So, I called the NYT and spoke to one of their ad reps. Now, for a full, black and white, inside page the price per column inch is 990 USD for a weekday and 1,120 USD for a Sunday. A full page in the NYT has 126 column inches. So doing the math, a week day, black and white, full page ad in the NYT would cost 124,740 USD. The cost of a Sunday full page, black and white, inside page is 141,120 USD.
These rates are variable, for example, color is a whole lot more. But if you could establish yourself as a non-profit organization you might be able to get a special, decreased rate.
Like I said in the previous post, there's a chance the editors of the NYT would look at the ad, decide it could yield defamation or invasion of privacry lawsuits and kill it before it'd ever got past production.