Agree the resale isn't great for SV6, I think this is partly due to ex rentals that are around, there are 2010 SV6's around for under $24,000 da, and that's with the dealer paying your rego transfer fee. Equivalent of paying $23,000 private sale. The dealer would also presumably be paying about $2,000 in GST, so as a trade in they are worth less than $20K. These cars are about 18 months old and new price for a new SV6 auto, with metallic pant is about $38,500.......so as a trade in they have depreciated about 50% in 18 months.
The upside is if you buy one of these, they are good value compared to new and the worst of the depreciation is already done.