Maybe, maybe not. Considering the factor of "What will people pay" still comes into play. Just because the 'vert would be cheaper doesn't necessarily mean it would sell more. While a 'vert is nice in some areas, there are still benefits to having a fixed roof, thus it might be worth more to me to pay more for a fixed roof.
I will agree that it would make for an interesting study if they were the same price. I think there would be a slight bump in vert sales. However, when you get into the $50K+ range for a car, I'm not entirely sure that coughing up an additional $5K for a vert is all that difficult. If you
really want it, then it's easy to justify. Just as it's easy to justify buying this new vette instead of last year's model or any other car for that matter.
"Low volume" is intentional. It artificially creates a higher price due to exclusivity. Think about it... all the R&D is done. Tooling and supply chains are in place. If Chevy decided to only mass produce ZR-1's, it could. And it could likely do it for only slightly more than the cost of the base Corvette. Sure, there are inherently more expensive parts on the ZR-1, but if the entire production assembly line of Corvettes consisted
only of ZR-1's, the volume produced would increase and the cost to GM would come down across the board. The end cost to buyers is intentionally
and artificially so much higher because, among other reasons, Chevy
chooses not to mass produce it.
I don't think I'm stating anything that's not pretty much already understood by most of us.