I think the idea of purchasing any magic item is linked to the newer, faster-paced modules that are coming out. When a character goes up a level or two within a short span of time, there isn't time to custom-craft items. At that point, the GM either says "no, you can't have it" (which is inherently unfair to some players) or says "yes, you can" (which is fair to all).
If there's time in my campaign, crafting and such is the preferred method. But if the players are in the middle of battling the Doom Cult from Hades and the wizard has been saving up for months/years for a Headband of Intellect, I'm not going to say no.
Interestingly, the crafting rules from the DMG2 (the ritual-based ones) mention _nothing_ of crafting time. The challenge you have to overcome, and the reward - those are both in there. But the time is short, which allows someone to actually make use of them.
If there's time in my campaign, crafting and such is the preferred method. But if the players are in the middle of battling the Doom Cult from Hades and the wizard has been saving up for months/years for a Headband of Intellect, I'm not going to say no.
Interestingly, the crafting rules from the DMG2 (the ritual-based ones) mention _nothing_ of crafting time. The challenge you have to overcome, and the reward - those are both in there. But the time is short, which allows someone to actually make use of them.