Except the S isn’t really a luxury car- it’s a premium car because of it having the latest EV drivetrain tech you can’t beat with any other offering.
You’re kidding yourself if you don’t think the huge deprecation on some of these MS isn’t in large part inherent to tech depreciation, which is now inferior to what you can get in much cheaper, “entry” M3, MY, or a new cheaper S. Less range, less acceleration in some cases, inferior HW and MCU, no heat pump, etc. Once more used M3 and MY hit the market, the used MS will further tech deprecate.
This is far different than the depreciation of conspicuous consumption luxury cars in which much of the value is tied to people knowing you have the latest expensive offering, even though it’s drivetrain and platform are shared with a lower trim or make.