No, $24k gross per year does not even begin to cover the amount of work put in to create and maintain software at the level of Pi-Hole. Not even remotely close. Not even 1/10th.
Pi-Hole should be making $1m ARR at least. 53 releases (going back to 2015), 2,765 issues on Github, multiple devs, supporting multiple platforms, extensive documentation, and on and on.
The top contributer has 500 commits since 2015. Its clearly a side project so $24,000 per year for a side project is very nice especially if you live somewhere with a good cost of living.
I have used a pi-hole based blocker for a while, and I have noticed increasingly ads showing up because they are using same domains, both in-app(iOS) and normal desktop. I've settled for a mix of network wide ad-block via pi-hole and adguard(uses mitm for https blocking) to remove almost all ads. In my experience uBlock Origin has made my aging laptop battery drain a lot quicker.
PS: I'm not sure if I would recommend Adguard, but works fine, but somehow the root certificate keeps me left a little bit dreary about possible future Adguard intentions.
Yes, it's an issue and there's nothing a pi-hole can do to solve the issue. YouTube is the most notable server of ads from content servers, but one can imagine more content providers following suit eventually.
However, you can have your pi-hole up and running in a few minutes and enjoy excellent network wide ad blocking for virtually every service that isn't YouTube.
Also related, I found by Bravia running Android tv would come to crawling halt if I used a pi-hole and loaded YouTube. I did the right thing by buying YouTube premium but still Youtube was doing aggressive pings back to their ad servers even with telemetry disabled. ¯\_(ツ)_/¯
Pi-hole will also catch all kinds of tracking and analytics requests that are sent via your mobile devices, non-browser apps, etc. There's a whole lot more of your data leaking out into the world than just the stuff that comes and goes via ad networks.
You only need to set it up once per network, instead of once per browser, and it is capable of filtering (most) ads even on closed platforms (e.g. apps on non-rooted phones).
The downside is that it is much less granular and harder to set up exceptions.
I'm not the maker of the app not can vouch for its integrity but you get a sense of how much network bandwidth ad and tracking takes up on your network.
This doesn't really explain how a PiHole compares to an ad blocking extension. Both block ads at the network level so your browser never has to download them.
There must be just way too much friction for a user to say, yeah, charge me $1/mo please.