Most of the low level items you can find in the market are also available for sale on NPC merchants or you can make it yourself.

I mention this because I was selling a lot of jewelry on the markets before I was aware of this, at prices much higher than the NPC merchants, and people were buying them like hotcakes. Once I found out, I reduced prices to the NPC price.

Someone pointed out that markets do provide one stop shopping and is much easier to identify upgrades, so perhaps a premium was reasonable. This is true - I find it much easier to go to the market and identify upgrades than go through my armory or recipes. And can often find good deals that are cheaper than I can make it, much less buy the item from an NPC. But I just wanted to mention this so newbies aren't ripped off because of lack of knowledge.