If all users use the same exit nodes (thus, same IP adresses), how can you calculate and apply VAT?
Regular payments are pretty much impossible, except for crypto, which excludes 99% of your potential customers. Add an .onion domain on top of that, and there's basically nothing left to gain in terms of profit.
Also, a list of the TOR exit nodes (IP's) is hosted on the official TOR project website:
https://check.torproject.org/torbulkexitlist
I'd bet most, if not all, affiliate programs have those IP's on their blacklist, which means, no affiliate sales either. Same for ad networks, and even some webmasters block TOR traffic.
I'm not a rocket scientist, but basic math tells me that I would lose around 99.999% of my income, if I'd swith to the TOR network today.