I feel like for every business there exists threshold where PMs get convinced that selling ads isn't just a free-tier business model, but rather that any other revenue generation method sits within the Pareto frontier that an ads tier defines.

I once heard an ads account PM put it this way: "If you have enough money to buy a no-ads tier, someone will pay more to put an ad there"

There are some for whom the paid tier is "get rid of ads". YouTube, Spotify.

In YT videos will still have "sponsored content" regardless. If they can't make YT display their ads, they will buy off the content creators. Ad industry is just so infectious.

SponsorBlock

It's also known that the extensions are also bought and start displaying ads, or worse, double charge the ad industry to let them escape their block (like once upon a time ABP did).

That has happened before, but very rarely, and I highly doubt will ever happen to SponsorBlock.

> That has happened before, but very rarely, and I highly doubt will ever happen to SponsorBlock.

Why do you doubt it? I've read that extension creators are constantly bombarded with offers to package just a little malware in their extension; surely the same is true of ads. If you're just a hobbyist developer—and that's where the best extensions come from—surely it's too much to expect that you'll resist that pressure forever.