I've pondered the seat leather refresh as well and given the cost I'm tempted to transplant some e46 sedan sport seats into my e53. It looks like hey have a similar beige / tan and I have read they bolt up and the seat controls / wiring are nearly plug and play.

Now to find the time to hunt seats...

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2013 X5 xDrive3.5i Premium
2002 530I Sport Package
2001 X5 4.4i
2001 M3