However, 10 years of 1 million domains, even if Google's cut is only $1 out of the registration price, is still $10 million per year * 10 years = $100 million.
If Google's own registry is used and you capture more of the ($17/year ?) domain fee, it goes up by multiples of that.
Correct me if I am wrong, but serving the DNS entries of .app will be almost the same as serving up a DNS entry for another domain like .com: the HSTS/https-only requirements will be set up in the browser, not the DNS server.
And serving DNS has been handled successfully and profitably by Namecheap/GoDaddy/Moniker et al for years.