In addition to Davidshek's awesome thread (with a poll!) be sure to check out LuigiHan's thread (also with a poll!). Those have both opened up a more general avenue of discussion regarding $3 songs, what would make a song worth $3 to you, and whether or not you'd ever consider buying 'the right song' for $3. More constructive discussion, less song specific discussion, less hostility, and less talk of economics.
Thanks to Davikshek and LuigiHan for creating an alternative to continue this discussion.