You can get a lot more than 10 levels through crafting. But it costs a lot of money. The people who did it during launch had entire guilds farming for them. Without having all the mats, leveling fast is not all that easy. I guess if you wanted to, you could buy gems, sell them for gold and buy the mats off the auction house, but it'd cost you.
But even during brief periods of crafting I've gained 3-4 levels. And there are 8 crafting professions. Conservatively, I'm pretty sure you could level more than halfway to max level just crafting...if you maxed out a crafting profession and then paid to change to a different one, until you did all eight. It's just not cost effective.