If there is such an unrealized margin why hasn’t it been eaten up by now? No one should be advertising on nyt at all if what you say is all thats going on.
Businesses don't want to pay for marketing that doesn't work and the simple answer is targeted ads work. Advertising to anyone that reads the New York Times, when a business can target people that are searching for a couple of key words relevant to the business' product? Even if it's the company's money and not my own, I'd rather spend it on something with a provable ROI, not just blindly blowing money showing ads to people that wouldn't or can't buy the product.
You are forgetting that the big tech ad companies are cooking the numbers in other ways making them generally untrustworthy. Ask yourself deep down do you trust Meta or Google.
The New York Times doesn't have to bullshit because people want to use it, thus it's a more trustworthy advertising point.