I usually hear that said about level 70 these days, although I really don't understand why people think they have to have a crafting profession. IMO, unless you're going for the BoP goodies in a given profession, it's easier just to have someone else make your item for you. And it's harder to make money with a crafting profession than it is with a gathering one, at least in my experience.
And if you check the trade forum, you'll notice that ohmikeghod is the reigning king of the "disenchanting=$$$" crew, although frankly enchanting's always seemed too much like work for me to take it up. Yeah, I'm lazy. I also like poking/hitting/blowing things up a lot more than using the AH for pretty much any timespan longer than about 2 minutes. I did try following his instructions for a while and they worked, but like I said, it just wasn't for me.
I find mining to be faster than skinning, because you don't really need to kill anything to get to nodes, unless there's a creep standing on it or something. If you're planning on becoming a beast-slaying monstrosity though, you might as well skin their sad little corpses once you're done sating your bloodlust, you monster.
I can't tell you whether skinning makes more money later on, but I do know that adamantium ore, for example, goes for over 20g a stack on my server, while the most I've ever seen any kind of leather stack go for is about 10g. Thorium is a nice moneyspinner too, because most people can't be bothered to hang out in the high-level Azeroth areas where it spawns because Outlands has such nice loot. That said, it goes for about 15-20g a stack here too, and its hilariously easy to farm, especially when you're over 60.
Honestly though, you can make money with just about any profession. Some are just harder than others.