I do not know about that, but if you search Ebay for Avast! , there are at least 50 offers between $5 and $20
Sure, but many of them are not legitimate. And if you are even able to find a legitimate one, the subscription will not be registered to buyer...
Eddy, who, in his own mind would pay $99.9 for an antivirus
Let's say that 0,01% of the people who do give me 1 cent today, I would be a millionaire tonight.

You might just as well ask “Who is paying for Windows if you can get a OS legally for free?”
If you buy a new system and it comes with Windows, you have paid for Windows as well, not just the system.