Personaly this is how I view the whole issue, too. I bought it for the fun factor, because it is beautiful, and because realistically I could never have the mount if it was achievement based ingame.

Strange how people forget the simple comparative that goes with all ingame trophies.
'Get it if you can, admire those who have it, don't QQ if its too hard to get yourself'

On the same basis I can start ranting about how unreasonable and unfair it is that Arthas' mount is only obtainable in that 1 way, but how hard would everyone laugh at me if I did?

Most every player on wow will never EVER get a chance to run heroic ICC raids, let alone have a chance at seeing that mount drop, how unfair is that, huh? How dare they? Oh but wait, it's supposed to be something special right? Just like, say, a vanity item bought with real world money, by those who CAN afford it?

If everyone just got over the 'Real Money Issue' they'd see that a lot of stuff ingame isn't necesarrily 'fair'. Because WoW isn't a socialistic environment, we don't all get the same things by default. Otherwise, why would proto drakes and frostbrood vanquishers be special and so awesome?

I am a player quite like yourself, i too play for the shiny things, for just having fun, i got a talbuk on multiple characters, i run old raids more then new raids these days 'cos some of the loot in there looks so great.. and well.. it's because of those things, and my way of playing the game, that i absolutely will NOT buy this celestial mount, the way i see it, it could very well lead the game down a path i don't want it to go..
today it's a mount, but what if tomorrow they offer a service which allows you to paint / customise your armor sets in exchange for real money?
it's ''just vanity'' but that vanity, a search for beautiful and cool looking stuff happens to be a big motvation in how and why i play the game, if many of those things will only be available to me if i put extra money on the table, then i'm not sure i'm interested in playing this game anymore.. i've played free to play games before where i payed money for fashion sets and other such things, but wow is a subscription based game, that's a totally different thing. you pay for the basic game, you pay for the expansions, and above all that you pay your monthly fees, why on earth would i have to pay even more for simple in-game items?! it just doesn't feel right.
the whole idea that it's owkay to charge extra because it's only vanity, is not very well thought-through, it's as important to me as any other aspect of the game, it's part of why i pay and play.