You're not making very much sense. :(
For one, they don't intend to sell this model in volume. 2-5k...maybe.
If they did, they wouldn't have waited to make it. So, perhaps you might rethink the target buyer for the Z?
The Corvette is a totally different car, marketed to an entirely different crowd. It is not competition, so strike it off the list.
The Nismo Nissan is different as well. The SS already outperforms it...so I don't understand how you'd consider it a bargain compared to a Z28?
The Cadillac...is again, different -- a 4-door, LUXURY sedan...not competition for the Z, and since you're taking issue with a 15k increase over a stock SS...how can you quote 9-14k more for a V as "competiton" Same for the last two you listed....
That leaves the GT500...anddd....the GT500. The performance of which costs roughly $45 grand. You can't get there for less. Honestly, unless they don't offer similar performance Z...I don't understand why it wouldn't (and shouldn't) cost in that same range.