gamestop has the music mixer disc (no microphone, but a live headset would work for it as well) for $1.99 - and how can you complain with that.. i dont know if thats online or just in-store, as the one that is closest to me has both the game disc and the official microphone for $1.99 each
grr, i paid 40 bucks for this when it first came out, just because i'm a sucker for perhiprials hehe
i paid 40 for the music maker when it first came out. some how I lost the dame mic adapter but was lucky to find someone who had it in my area and she game it to me. but now and then gamestop has the mic and adapter for .99
and the game is 1.99 but no seemed to use it that often. so i guess they decided to quit making content. I havent tried it yet but i beleave you can rip kcd to the drive and use them with the program as well.