$70k looks to be in the current range for an '18 CPO comp. Maybe try to negotiate for a few off.
Consider <$10k up from there are M3 CS. Worth the price jump, imo.
If you want a glimpse at real market value, i.e., the initial drive off the lot loss at whatever purchase price, run the vin through the vroom and carvana quote systems.
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M4 GTS, GT3, C63 S | E90 M3s, E39 M5
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