Next stop sub $4k?  

Most definitely. A very popular Pro release such as ACDC could go down to a third of release price due to numbers. They will then hold value over time. I remember the same trend when I purchased my used Flash in 1980. Picked it up for $600 when they were selling new for about 2K. They were so popular that every suburb had a half dozen of them in the wild. There were bargains to be made on the used market.
Have you made any analysis on the LE market trends yet. It would be interesting to see how they hold their value.

Home collector Pro prices should also hold better value than heavy played operator equivalents.