On my server there is another gold-crafting blogger (breevok), that sometimes we work co-operatively, and sometimes competitively. We had a discussion earlier tonight about arrows , a low markup, high volume area. At the moment, the prices of arrows are 5g per stack, where midweek they were 1g50. As I don't have an arrow manufacturer, I often just buy his arrows, and re-sell them. I pointed out that his main competition was offline, and that he was selling above market. He asked if I was going to undercut him, and my response was, "I couldn't be stuffed". This is especially true as (a) he was online so could immediately re-undercut me, and (b) my arrows were on another toon.
While I was on my next bank alt, I was posting my bits and peices, and noticed that someone had moved into 'My' market for Rituals of the new moon. Last time I looked, I had no real competition, now I had stacks of it. My main competition is Puraa, one of breevok's alts.
There is nothing personal about this competition, it is just business. I am going to try maximise my gold/hour. Sometimes, this will mean that I will undercut (in this instance - it means selling an offhand for a profit - at market value). Other times it means not playing in a highly competitive market and moving somewhere else (I've just picked up the recipee for bag of jewels - where there appears to only be a few sellers). In any case, if it wasn't an associate (in the form of puraa/breevok), it would have been someone else (pandapanda for example), as offhands are a good way to consume snowfall inks. I fully expect Breevok - and others, to do exactly the same thing.
If you want to make money by selling things, keep an eye on your markets. If someone else starts playing in your corner, that's OK. You may decide to keep playing with the newcomer. But explore other possibilities.
P.s. Congratulations to Breevok for his gold cap. I did call him a cow, but it's only because I am jealous.