If you're implying that lvl 40's make more money and therefore can afford to buy the materials to power level their crafting, then I would say that is because the value of materials is too low. If crafting was more profitable (by being more useful/required), so would gathering. The gap between grinding level 40 monsters vs gathering resources would be much less.
However i'll go back on my point and say that personally, because the population is low, that it is simply not possible to buy your way to 40 in a craft all the way. There is not nearly enough supply of resources to get the amount you need, at best you can buy all of your secondary resources (coal) and then you have to gather the rest yourself.
You certainly don't level "twice as fast" unless you're talking about a skill that requires you to kill monsters (like skinning).
Edited by Malthrus, 02 March 2014 - 19:03.