I think MB depreciate as fast, or faster then BMWs given what you got the s550 for.
The poor sucker before me took a nearly 45% depreciation. If I keep the car for 5 years and then sell it, the pain is acceptable. For what it's worth, the 7 series resale is the worst I've seen in years. If you want data to support it, I can email. My neighbor leased his 7 series in 2006 for 3 years. After 18 months, he had enough, exercised out of the lease early, took a bath on it and bought an MB - he has sworn off Beemers for life.
Here is a sampling of west coast 2007 7 series resale...
08/19/09 BAY CITI Lease $42,750 22,993 Above JET BLAC 8G A Yes
08/19/09 BAY CITI Lease $42,000 33,172 Above MICHIGAN 8G A Yes
08/19/09 BAY CITI Lease $42,000 20,724 Above JET BLAC 8G A Yes
08/19/09 BAY CITI Lease $41,500 19,851 Above KALAHARI 8G A Yes
08/19/09 BAY CITI Lease $41,000 19,750 Avg TITANIUM 8G A Yes
08/19/09 BAY CITI Lease $37,000 43,343 Avg TITANIUM 8G A Yes
08/27/09 RIVRSIDE Lease $41,500 20,089 Above ALPINE W 8G A Yes
08/27/09 RIVRSIDE Lease $41,500 19,674 Above JETBLACK 8G A Yes
08/27/09 RIVRSIDE Factory $40,500 15,995 Avg TITANIUM 8G A Yes
08/27/09 RIVRSIDE Lease $37,500 37,886 Avg JET BLAC 8G A Yes
09/04/09 NEVADA Lease $43,750 21,444 Above TITANSLV 8G A Yes
09/04/09 NEVADA Lease $37,000 40,878 Avg TITANGRY 8G A Yes
I still like the Z8s:biggrin