Residual value on luxury cars is mainly bad because the maintenance costs on a luxury brand cars quickly go into the stratosphere after the factory warranty runs out. When the warranty is running out, you're hitting time for new tires, brakes, etc. It all raises the cost of a second hand BMW to be almost as high as a brand new one.

The way to "hack" this is to either stop going to the dealer after your luxury car goes out of warranty and find an independent mechanic or work on your car yourself. Both have their own drawbacks, but it's generally what you see most long term luxury car owners doing.