I saw a 03 4.6is recently at the dealer that I bought my E38 from - had over 100K miles and they were asking $22K for it, something like that. KBB pegs it at $17K. So maybe not all that crazy, tho 143K is getting up there.

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2003 4.6is - SOLD
2003 M5 Imola
2008 Mini Cooper S
2011 Mazda CX9