Apple is luxury big tech.
In this day and age, privacy is luxury, so that's what they sell.
I don't think there are any ethical motivations for them (or any other large corporation - none of them have morals so they cannot act morally). It's just that there's a market niche, so it will be filled by someone.
It’s an additional layer of wall for their walled garden to keep the technically proficient users that are more likely to hop walls.
money from advertising basically dwarf user lifetime purchase of privacy tax you mentioned
The ad business has a lot of people chasing after the same ad spend.
Superbowl ads, TV ads, radio ads, print ads, billboard ads, public transit ads, youtube ads, podcast ads, search ads, e-mail ads, social media ads, in-app ads, in-store ads, sports team sponsorship, individual athlete sponsorship, stadium naming, product placement ads, elevator ads, cinema ads, bathroom ads.
And Coca-Cola doesn't increase their advertising budget just because someone finds a new place to slap ads on - they just re-allocate their spending.
Sure, Google and Facebook make a good chunk of money from ads. But it's a very, very competitive business.