not quite. hourly rate and amount of time spent to make the asset is something that is only relevant to the scenario of custom-made art for one client.
in short…
you say: if I spend 2 hours working on an asset and have an hourly rate of $15, I sell it for $30
I say: if I spend 2 hours working on an asset and have an hourly rate of $15 and sell it for $30, and I sell 10 copies of my asset, then my hourly rate became $150
before the thread dies and hoping I can guide it back on topic,
I would like to agree with one view expressed here. if you don’t like it don’t buy it. I’ve seen some of the marketplace stuff that I might buy and some that I know I definately won’t buy.
even if I didn’t own WorldMachine I’d never buy any terrain. not only because my game might look similar to another guy’s game, but because then my game’s world layout becomes limited to what the original terrain artist depicted, not what I want for it. and editing the terrain will only work a little bit before some stuff will be completely off (flow map, depo map, color map, and a big etc)
the actual problem for judging before buying is the marketplace has only a few well-placed and staged pictures of the assets so sometimes it’s misleading
potential solution: require much more preview material for all assets. a video at least, more technical images (wireframes, physics views, etc). maybe also an html5 preview (but then you can reverse engineer them I guess)