Jimmy,
After just returning from a business trip to the left coast I am admittedly groggy this morning and had not yet had my 1st cup of coffee when I posted this response.
No doubt you are correct about Sandy Koufax's milestone last pitch balls. Given Koufax's crossover popularity, etc., I would concur that we would see five figure prices in a major auction for his milestone balls.
Thanks for keeping me honest!