To a rough approximation, that's footed by the 1 billion wealthy inhabitants of the EU, US, Japan, Canada, Australian, and New Zealand. (I said rough, roll with me.)
That means that the per person costs of advertising are pretty much $100 annually online and $600 annually for all content (mostly TV). Keep in mind, those are real expenses expressed through household purchases.
(This means, by the way, that online content isn't free, you are paying for it, only, you're doing so indirectly, through advertisers.)
By contrast, total direct expenditures on print media run about $125/person in the US. (Audio/video may add to that.)
If you look at what is advertised, an awful lot is very high-ticket items. The FIRE industries (finance, insurance, real estate) were the largest chunk of spend as of a couple-three years ago. Electronics is another large segment.
The notion of some sort of universal content payments scheme, preferably indexed to wealth and income, has a great deal of economic justification. I've been exploring that for the past few years.
https://www.reddit.com/r/dredmorbius/search?q=universal+cont...
But yes, the dynamics are a tad bent.
There's no implication that every dollar they spend on marketing directly translates into $10 of new spending "that they would otherwise not get at all".
Much of it is brand spending. Procter & Gamble is the world's largest advertiser, and the goal of their ads is to make sure you keep picking up Tide every time you're in the detergent aisle. Coca-Cola's ads aren't trying to get you to buy $10 more of soda than last week, just to keep soda on your shopping list every week. Those ad dollars would need to be replaced by the subscription if you're going to remove the ads but keep compensation for the websites the same.
And that's just not realistic. One-off purchases, maybe. Sustained 1k/hh/mth avg - I'd love to see a proof of that.