One time alignment where I'm at is $80-90. At BMW dealer you can probably multiply that by 3. I got 5-year unlimited alignment for $189 from NTB and they didn't have a problem with straightening up the rears for me outside of spec. Well I say straighten but were only able to get them down to -1.7 . . . straighter than they were. There is nothing special about the X to where it can't be aligned at any reputable alignment shop.

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2010 Lexus RX350 still new
2003 BMW X5 3.0i w/sport package w/68K miles. (gone Thank God!)
2002 Dodge Ram 2500 4X4 cummins diesel w/198K miles, custom repo truck
2009 Scion tC w/46K miles
2007 Suzuki SV650 custom streetfighter
2000 Lexus GS400 w/165K miles