Character boost is meant to be optional, not compulsory
'The character boost we get for buying Warlords of Draenor is intended to entice older players who've stopped playing, but who want to come back, to make the decision to do so. One of the barriers to this is the fact that they stopped one or two or more expansions ago. They're sitting at 70, or 80, and their friends who kept playing are at 90 and will be able to go straight to Draenor when Warlords drops. Without this feature, the hypothetical returning player would have to level through Wrath or Cataclysm to catch up to Mists content, and thus couldn't play with their old friends. This makes them less likely to come back, because they're too far behind. The character boost feature says that they don't have to worry about that - they buy the expansion, and immediately they're boosted to 90 and given decent starter gear to head to Draenor with.
Now, like all features added to World of Warcraft, there are other uses for this feature. If you have a stubborn alt you just can't get past Cataclysm, now you don't have to. And that's great. But that's not what the feature is designed to do. It's just a happy accident of the feature that it can be used for all sorts of other players. You want to test out that rogue and maybe switch mains, but have never played a rogue and don't want to have to grind all the way up from level 1? Boom. You have that bank alt who you've wanted to give a shot for a while but can't stand the idea of doing The Burning Crusade content for the sixteenth time? There you go. And it is these possibilities that have led to the fact that, as Blizzard admitted at BlizzCon, players are going to potentially want more than one of these character boosts. Thus, the effort to make it a feature you can purchase from the game store.
We've covered this before, of course. The reason I'm mentioning it now is to set up the context for the feature's ultimate price. Whatever it ends up being - whether it ends up at $60, or $30, or more or less - the purpose of the feature isn't to allow all players to forever skip 1 to 90 content.
The purpose of the free boost with Warlords of Draenor is to allow returning players to catch up with their friends. The purpose of the purchased boost is Blizzard's recognition that without it, people were going to buy another copy of Warlords, use the already existing character transfer service twice, and use their second account to boost another character. How much would that cost? Well, it would cost you $50 just for the two character transfers. It would also cost you the price of World of Warcraft and all expansions including the new expansion - let's say $25 for all WoW up to Mists, another $25 for Mists (it might get rolled into the battle chest at some point, but for now, assume that you have to buy it) and $40 for Warlords. That's around $90, plus $50 for two character transfers. So Blizzard saw that people were talking about doing this, calculated the price at around $140, and said that's very convoluted, we'll have to offer a simpler way to do this and the price they set for it is less than half what people at BlizzCon said they were willing to pay.
To my eyes, the price at $60 is an absolute steal. Even if we assume that players will be able to get Mists of Pandaria rolled into the battle chest, dropping $25 from my estimate, that's still $115. Even if you left the character on the second account, you're looking at $90. So the price we briefly saw this feature at is thirty dollars cheaper than the cheapest option possible if they had never offered it.
We need to ask ourselves this - how much should it cost? Having it as a free option as part of the expansion to get returning players caught up with their friends is one thing, but how much should you have to pay for a feature to allow you to skip out on the majority of the game's content? How much is your own time worth? How much should it cost to keep leveling a viable option? Too cheap, and this becomes practically required - a $15 boost basically demands that you use it. At $60, you probably won't use it, unless you really really want that level 90 now or just can't stand the idea of running Hellfire Peninsula again on your legion of alts. But now it's not only an option, it's a costly one - and yet, still far, far cheaper than it would be to buy a second copy of Warlords and move the character back and forth.
This is my take. Yours? Well, that's what the comments are for.