You are only telling part of the story...
Don't forget to add the $15 shipping to all those prices. That brings the total average to $494. That is the price I expect to equal or beat with more participants. Also, some of those units are used, these are all new. The first unit I bid on E-bay went for $635 (I bid $625). I wish I had found this group buy earlier.

Dear ttonyztt, you were not the winning bidder on the following closed item:

Item Name: Rio Car 10GB MP3 Player Model RD100-10 New (Item# 1360887867)
Final Price: $635.00
Your Max Bid: $625.00
End Date: Jun-22-02 17:03 PDT

If I don't have at least 10 people in the group buy, I'm going to buy the rest of the units myself.