here's a payscale i'd like. i'm basing it kind of off what i'm willing to pay for iphone applications, since that's the closest to micro-transactions i get right now.
$10-$15 : extra special avatar - wild and crazy unique avatar packages. be a robot. be a dinosaur. be whatever race uncle friendly is. concepts that stretch the concept of "humanoid" just a little bit. different body type so normal clothes wouldn't work on these avatars. thus, they'd have their own special clothing sets. you'd get a basic clothing set for free [3 or 4] with the avatar, but could buy new outfits for 5 bucks a pop [like formalwear or biker clothes]. there might be some things that these avatars might not be able to do anatomically that "normal" avatars can do [like climb certain things, swim etc. etc.] burt the extra special avatars would have unique, compensatory abilities.
$5 : merely special avatar - a slightly different head and texture on the basic frame. here we'd have orcs, werewolves, cat people, deer people, devils and assorted other humanoid races. "normal" outfits would fit on these avatars just fine, though i think it'd be cool if some of these avatars had tails which might work with some outfits and not others. these creatures could have some unique abilities, animations, jumps, skills etc.
$0 : standard avatars - humans and pointy eared humans
$0 : basic clothing
$1 : an article of awesome clothing
$5 : a matched set of awesome clothing
$0 : basic decorative item for a house.
$1 : cool decorative item for a house
$5 : set of matched decorative items for a house
$25 - $50 : a house [depends on style, size, location]