I think the problem is selling icons isn't because it relies on the honor system--if we did such a thing (NOT THAT WE SHOULD), I think it'd be pretty easy to have the icons we sell have hash values that are checked when somebody uploads an icon and not allow them to upload it unless they've bought it. Which doesn't prevent them from using it on, say, LiveJournal, but it could be prevented on DW itself.

The problem is that the main portions of the culture around the making and exchange of icons is a gift economy, and thus attaching and enforcing a monetary value to specific icons by DW would, to many people, feel very disrespectful and tone deaf.