How would you base it on $15 a month? Do you assume the player will play five years? So the average would be $900 per person. So what would prices on the items be $30-$50 a piece for every little thing? You can probably do $10 per major item if it only unlocks on one character. Because the problem with buying stuff is it…
Well your idea of play to win is wrong to start off with. Pay to win means having an UNFAIR advantage over another person who can not over come this advantage through normal gameplay. So that makes your whole point invalid. I don't know of many F2P games that don't have some form of what you describe, SWTOR, Eve Online,…
What are you smoking? Even if your example was true, that 1 server is not one server once you begin instancing you usually add more servers. So essentially your still adding servers you just making it appear to be one server. Which if your going to do that you might as well open up whole new realms.