The staggered tyre sizes on recent Vettes combined with GMs lack of supply make tyre shopping a nightmare over here. Correct runflats are scarce and even in conventional tyres it can be hard to get a matched set of anything. I have a recent set of Michelin PS4S on the C7 which came in at about half the cost you've highlighted above for the new Z06. If the tyre supplier does "vulcanised" repairs and odd nail or screw isn't too punishing.