I can't tell whether you're being sarcastic or not. All you've achieved is to (yet again) push the tracking to a different part of the URL - presenting: tracker-12345.com
Yeah, it'll cost me $5/year or whatever. Assuming I can't get free domains*. So all I need to do is add $20 to the price when I'm selling all your data and then cancel the domain after 3 years of inactivity.
Also blocking subdomains would cause a bunch of headaches. Having to register a new domain for my-app.com rather than using myapp.mycompany.com shouldn't be necessary and would be a pain for all the little guys out there.
The fact that there's money involved now means that this scheme would disproportionately affect individuals / small / open source projects while leaving the huge corporates (who are the ones doing the most tracking and slurping the most data) almost unaffected.
*if I'm large enough, I'll just buy a TLD (or use the one i already have, *cough* .google *cough* .amazon) and not pay that $5/year/user in the first place.