hmm just giving my opinions
safezone is indeed valuable to the end users - it provides additional banking security compared to the free version.
u might say that if a system is already compromised, u will not trust the system for banking anymore. but what happens if u do not know that ur system is infected? a user who bothers to learn how to use safezone for banking purposes might just be able to protect his personal information even if the system he is using is infected. (i am not saying that safezone is impenetrable , but it is another useful layer to protect ur personal infomation)
so, if u often use ur computer for banking, there is a chance that u would like this additional protection. if so, it is reasonable to ask u to pay a subscription fee for the continuous research and development they put in to create safezone (avast does add new features/improve safezone from time to time, eg. the next version would allow the use of 3rd party password management tools like lastpass...etc)
on the whole, i feel what avast is doing is well within the industry standard - u subscribe for the continuous improvements to safezone (a kind of program update, while not as frequent as definition updates, is definitely something much more worthy of a subscription compared to that for definition updates. this is because definition updates offer ineffective protection against today's malware - u know that no antivirus can rely on definitions alone for 100% protection. whereas safezone in theory, should protect the user from all malware)
however, the thing that matters the most is that avast is profitable. if not, all discussion is moot