That's been going on for weeks now, to be honest. I think it's a matter of courtesy, really. If someone is saying they're selling/buying/etc you don't go right after them and try to undercut them or 'steal' it from them. Plus it comes across as rather desperate when you do it, and the resulting town 'fights' are kind of... mm... remind me of children on the playground "No it's my turn now!" or "No I want them on my team!".