Those numbers are a big deal, because its all mindshare.
HDDVD hasnt lost a single release yet and BRD hasnt gained one, and yet the mindshare shifted so dramatically that BRD quadrupaled HDDVD sales when previously they were only doing 50-80% more. My guess is its a combination of HDDVD owners not running out and buying anything, and PS3 owners who have been on the fence deciding they are safe to buy movies now.
Edit: I'm keeping my collection. Between hardware and moves Im allready well over 1000 dollars invested in this, probably closer to 2. I doubt I could even get 500 for the set at this point. I'll just hold onto them, the movies work just fine, and if Sammy gets their dual format player up and running, I wont have any issues playing the movies.