Oh yeah, 9 out of 10 times buying is always the sane option, it simply takes absurd amount of orbs and luck to craft something properly.
This is what keeps those in the know in exalts. If you are trying to craft something from a white base, it is going to be expensive as hell, because you'll probably scour the item after using exalts on it (trying to get perfect or wanted mods).
I've made a ton of great gear, including a 57 IIR ring with 20 all resists 60 life and crit. Here's how I mainly craft :
1. Look for weapons with flat physical damage and other good rolls. For example, I pick up all blue Harbinger bows and ID them. If they have flat phys like 'adds 30-50 physical' and another good roll (attack speed, crit), I'll save it in a 'crafting tab'. Ilvl 77 is best, but you can still make insanely high damage bows with lower ivls.
Regals are like candy once you start doing high level maps, so I'll regal the bow in the example above to see if I get another great roll. If so, I'll either exalt it for more mods, or use the Elreon multiple crafted mods on it. If the regal added mod sucks, I'll vendor it.
2. Pick up ALL gold rings and amulets. That one out of one hundred that has double IIR rolls - regal for sure. You can make better IIR rings from these than Andivirus (sp?).
3. Armor is worthless unless it's 5 or 6 linked, so even if you find something with 110 health and three 40%+ resists, it sucks. Trying to 6L something will cost a LOT of orbs, unless your extremely lucky.
The better way is to buy a white or cheap 6L, then spend 100 chaos orbs on it to get great rolls. Instead of spending 1500 fusings (around 22 exalts worth) on Vorici to 6L, or even 500 if you are lucky (7 exalts); 100 chaos orbs (2.5 exalts) is cheap (and easy if you do the chaos orb recipe).