The Superformance Cobra Owners Forum (SCOF) has a table tracking the base price history for their turnkey-minus rollers --
CLICK HERE. Final selling prices depend on drivetrain choice, options, labour and so on.
I started tracking "asking prices" for used SPF Cobras listed here and on Cobra Country. I
started a thread here which I update from time to time. Take it for what it's worth.