Now, I like to make things in video games when given the chance. Last time I played Final Fantasy XI I hardly killed any mobs at all. I played a lot, but I spent my time almost exclusively crafting. Diablo III has a couple of different ways to craft but they were all incredibly stupid at launch. I don't know if it was a problem with the AH being new or what, but it didn't make any sense to make your own stuff. The question is, does it now?
First stop, gems. Does it make sense to level up to the top tier of gems on your own, or would you be better off selling the gems you find and buying the best stuff on the AH? Does it make sense to crush your gems and sell them on the AH yourself even accounting for the 15% cut. I ran the numbers in a spreadsheet and for the most part you don't want to do either thing. The 15% cut makes it so it's not worth selling anything beyond the first level of crushed items, and then only if you want to sell off your gems/tomes. I don't want rubies, so I'm doing that. If you do want a high level gem you're better off making your own, which is nice.
Next, salvaging. Do you want to vendor all the gear you pick up, or salvage it for parts? Do you want to pick up blues? Well, it would seem that the salvaged stuff has settled into a nice spot where it's right to salvage the cheap stuff and vendor the expensive stuff (and then buy salvaged mats on the AH if you want them). I tried to do this for a while, but it was adding too much time to my 'in town' time. So for now while I need money I'm just going to vendor everything. If I run out of my stash of materials then maybe I'll reconsider. I'm also not picking up blues, but I think if I was salvaging everything I would.
Finally, crafting. Most of the stuff back in the day was too low level to be worth making, and I think that's still true of the old stuff. But they've added some new patterns in the last patch which are totally worth making if you don't have a nutty item in that slot. I actually think the int+5 bracer pattern I found is possibly best in slot. I made a really good set with crit chance which makes me happy. These are bind on account, and are made with a bind on account material, so I will probably make more just to use up the stuff I find in case I get a truly awesome thing.