It depends, I have around 11 posts removed so far (a bit over an year on the forum now), but in this list are posts removed from self-moderated threads (just went trough my PM history). So those removed posts in the self-moderated threads are also listed in the modlog, seems like it, this will be a bit of an issue then.
The idea of evil IPs and paid memberships is already enough. I wonder why you think deleted posts should attract a fee; not that its a bad idea but a ban should be sufficient after being warned severally about your off-topic posts
Because it will be automated, so less work for the mods in the fight with the bots. If we get them banned, this would be the perfect solution of course, but the reality is different, most of them escape the ban and just continue spamming.