Indeed, ads aren't charity. If companies are spending $1,000 per adult in the United States for advertising (which the are, from the figures I can find), that's because they either:

A. Expect the ads will manipulate spending habits to bring in more than $1,000 of profits per adult on average (with the actual spending needed to reach that profit being far in excess of $1,000, considering profit is only a fraction of revenue).

B. Don't expect the ads to manipulate spending habits, but are stuck in game theory hell where companies waste a vaste amount of resources (10x the budget of NASA) merely to maintain the status quo, because any company that doesn't will fall behind its rivals.

C. Some mixture of A and B.

The cost to the public is mental intrusion (if mental intrusion didn't work, companies wouldn't buy ads), financial (in case A), and also the bad habits that advertising companies and the companies that deliver them push on us so that we can consume more (sedentary culture of watching TV to consume more ads, mindless browsing to consume more ads, encouraging political fights with family to increase engagement and consume more ads).

It's hard to not come to the conclusion that advertising is a huge blight on modern society, and exactly the kind of thing collective action by a society should be fighting against.

Unfortunately the ticket covers much less than the infrastructure cost. Then public spending covers some of it but ads are needed to fill the gap. Public money that would be spent to cover the ad revenue would not be spent elsewhere (in a hopefully useful way). I hate subway ads just as much as you, but wanted to make this reality check.