IMO the price drop in the D2s is most likely driven by the perceived maintenance costs and people's fear of paying too much in maintenance vs the cost of the vehicle.
If you consider the average decent mechanic charges $120/hour or more in Sydney then it doesn't take long to rack up $1000 in labour only, Then add to that shop supplies, disposal of oils and parts you can see how quickly it adds up. Years ago more people did their own maintenance, the cars were simpler then - less electronics. At the end of they didn't see the need to go to a mechanic. Their approach was why pay someone to do something that they could do.
If you can tackle some of the basics for maintenance and repairs then that reduces the pain in the wallet when something major happens - a bit like saving for a rainy day. To what level you do the basics is driven by how much you know mechanically, how much you want to learn and how much you have to spend.
At the end of the day the D2s are still very capable for their age. Unfortunately if you are trying to sell one then that isn't being reflected in the current used prices.

