Sure the basis is the same: lacking knowledge. One is the inability to acquire it, the other is the apathy to acquiring it. You're one of these and I haven't decided which yet.
Well, sure, you get what you pay for, but at least they're better than nothing. And really, what do the paid versions do that the free ones don't? OOH if I pay for AVG's pro version I can schedule tests. Or, I can hit "run complete test" whenever I feel like it.
AVG is every bit as good as Norton. It's not they're going to say "oh well he isn't paying for it so we'll just make sure we leave some of these virii out of the definitions, that'll teach him". Great business acumen that would be wouldn't it?
I'm not going to say you're stupid to pay for stuff, no, whatever your preference is is fine. But at the same time if you're trying to make a point you need to do better than "Norton caught 14 viruses AVG didn't" with no proof of any kind.
Besides, it's not like AVG is the ONLY thing I'd run. I use AVG, Spybot Search and Destroy, Ad-Aware 6, Norton Utilities (ah there's one of them "not-free" programs), Sygate firewall, and I am behind a router. Very little happens without my knowing it. I don't think I could get any better protection by paying for all this.