So the parts prices don't look too bad, and as someone said, brakes should be the least of my concerns. On the service records I have looked at on a couple used examples, 29k seems like a point where it might need fronts.

My biggest challenge is getting the price right on a used one. I missed a 2010 with 29k miles for $60k a couple weeks ago, and it wound up at a BMW dealer who then listed it for $71k. I looked at one with 44k miles locally and they raised the price to above mkt. after I looked at it and they discovered it had a whole bunch of options. Luckily time is on my side right now.

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2016 GMC Sierra 2500 HD All-Terrain, Duramax 6.6

2011 X5M Alpine White/Sakhir Orange, Eucalyptus, Spare tire!, Comfort, Soft Close, Tech, Rear Climate, Individual dash, Individual Audio, HUD, DVD, USB, Cold.

Gone:
2008 4.8i
2005 X5 4.8is
2004 X5 4.4i Sport
2004 X3 3.0i 6MT
2002 M5