Alfa sold 5700 GTV6s in the USA, only 35 of which were Callaways(less than 1% of production). Callaways were blessed by the factory and were sold by Alfa dealers with the usual Alfa warranty. Callaways had 50% more HP and torque and very little additional weight. They're very rare cars that very rarely come up for sale. In my opinion the best examples - like this one- are six figure cars.
Opinion is one thing (especially if you'r not buying), fact is another. If someone actually has $100,000 to spend and buys this car for that sum, then it's worth $100,000. Otherwise, it's not. That's all I'm saying. As of yesterday, there's no evidence this car is worth more than $42,500. If it sells elsewhere for a larger sum, I really would love to hear about it as it'd be a historic day got GTV-6's of any kind.
As a side note, my friend (Griffo on the BB) is working on a GTV-6 registry. It'd be interesting to know how many GTV-6's are currently on the road (read: at least registered) in the US. We both figured it can't be more than 1,500 and likely is under 1,000.