Know any good writing that introduces the game item market to outsiders? I am curious about the thought process of people who spend money in this way, and their perception of value.

I imagine a taxonomy of motivations, like the one Larry Harris has in _Trading & Exchanges_. Presumably some people get entertainment value (because surely there is a kick in seeing a game's world modified beyond its normal rules of state mutation); some speculate on price trends (hence the price graph on opskins.com; what are time series graphs for if not to spark idle dreams of avarice), and others getting some sort of utility (i.e., money laundering).