They're asking way too high. Normal Z8s are going for $150k+ but even Alpinas aren't that expensive. Hell BaT sold an Alpina in June for $352.5k.
https://bringatrailer.com/bmw/z8/?q=z8
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'07 Montego Blue/Saddle Brown E92 335i - 6spd. -
Regretfully SOLD
'16 Carbon Black Metallic F10 535i M-Sport -
TOTALED 11/21/21 
'13 Black Sapphire Metallic F30 335i M-Sport - unknown charge pipe, MSport Exhaust, 20" 405M wheels, $61k MSRP, CF M4 Mirror caps & Spoiler, NGK plugs, Dinan Coils, BMS intake