I don't believe that the owner is funding this site out of his own pocket year on year. For the minimal amount of interest he shows in it, it doesn't make sense that he would just keep throwing money down the drain to keep it running. He'll be making at least a majority of his money back somewhere along the line.

I won't pay extra, but if people want to pay for some extra features then there's no reason to have a problem with that, I suppose.

You'll also have the potential conflict of interest when it comes to giving long bans to paying members, which could cause more hassle than it's worth. The site is either full of "which fm do you love most" in a variety of different disguises, or "which flawless pop bitch is going to slay/shade another fierce pop bitch with a black person picture", so charge away, but the fundamental issue here, as always, is going to be attracting and keeping new members.