I played World of Warcraft on and off for a few years. I was a pretty hardcore player from the launch of Burning Crusade through to near the end of Lich King and came back casual for a while for late Cataclysm and early Pandaria. I know the game pretty well and have friends who still play it.
So I can say with confidence that you would be absolutely mad to pay for a boost up to level 90 with prices like that (and if you are a new player, mad to pay at all).
There are two types of people now who might be starting out at level 1; new (or returning-after-a-gap-of-years) players starting their first characters, or veterans levelling an "alt" (a secondary - or indeed tertiary or beyond - character).
If you are a new player, then going through the level-up process is important and you should not skip it. First of all, this is where you learn how to play your character. Most end-game content involves group-play and if you have a brand new player at the level cap staring at a hotbar full of unfamiliar abilities, it will be a long time before you are actually competent enough to play alongside others. The level-up process, during which you are introduced to abilities one or two at a time, takes you at least part of the way along that learning curve for your character. It also exposes you to a lot of the game's lore, if that's your bag (I always found WoW's lore a bit boring and juvenile, but some people like it).
And if you're a veteran player, then there are lots and lots of things you can do to accelerate the level-up process for an alt without handing over real-money. I levelled up three alts while never taking them out of "rested" state (meaning they were getting double xp from kills). Heirlooms allow you to boost the rate of xp gain even faster, to the point where 1-80, by the launch of Pandaria, was just stupidly fast. I doubt even a brand new character takes over 100 hours of game time (or indeed, anything like it). Alts certainly take much less.
So yeah, I can't imagine Blizzard would have too many takers for this. Or at least, I hope they won't.
You learn very little in the leveling up process in today's game. People who say otherwise are stubborn and believe you should suffer the slow process like they did in 2004. Once you hit max level everything changes. There's guides, macros, priority lists, addons, etc that allow you to learn your class quickly and efficiently. Yet WoW still has tons of bad players. So forcing someone to spend extra "wasted" time leveling isn't going to fix them.