It's been over five years since Horse Armor, and still, developers and publishers are struggling with how much to charge for downloadable content. Just ask EVE Online developers CCP. They've got no idea.
A new EVE Online store opened this week (along with major new updates like an interactive "Captain's Quarters"), with a new currency to go along with it, allowing players to purchase "vanity items" for their shiny, impressive new character portraits. While CCP admirably have said that the new store would not allow microtransactions to be purchased that impact gameplay in any way, the stuff that is on offer has to be seen to be believed.
At the current going rate, using the existing currency (ISK) and transferring it to this new currency (PLEX), a skirt for your avatar costs USD$20. A blouse is $25. A space monocle costs $68. As Massively points out, many of the items on sale are going for more than their real-world counterparts would in a store, making it only more tragic.
Note that ISK can, if you want to do things the hard way, be accrued just by spending time in the game.
While none of this stuff is compulsory in any way, and is targeted at EVE tragics who have more money than sense, you'd think CCP would have been a little more subtle about fleecing the devoted.
Controversy brewing over EVE Online microtransactions [Massively]