Post hoc ergo propter hoc.
Doesn't quite fit this scenario perfectly, but use your imagination. Him having not contributed does not in any way, shape or form imply anything of his intelligence. You were quite wrong. I will reiterate, paraphrasing, what I stated: The daemons to run a Warcraft server are not resource hogs unless you have a significant population load. An average, consumer-level PC of today (And for the past 5 or so years for that matter) can handle a decent number of players. I cannot answer definitively how many players would break the, say, 5GB of actively used (Not reserved) memory threshold since that would be impossible and differ from machine to machine (As no 2 pieces of hardware are identical).
I should define my use of significant: 10,000+. Yes, 10,000. That's just a ballpark but I can say a very high number because system resources have absolutely zero bearing on if your PC can handle a server. Your uplink speed is what matters because chances are, unless you have Google Fiber, you will max out your bandwidth well before ever, ever, coming near maxing out your hardware. Unless of course, you have a fuckton of malware.
I have personally hosted many game servers for various games across the genre market, most often reaching a decent number of players, relative to the number of people who actually play the official servers, which was often a pretty low number. With the exception of a few really crappy cores, I've never maxed out my hardware resources. Off topic, but do you know how pissed off people get in FPS games when you start maxing out your bandwidth?