Well it always depends on the person:
If you enjoy flying and have the money to spend I see no issue in booking such a last minute mileage run to get *G. Money spent on something you enjoy, even if it's a last minute short trip to New York, is not wasted money.
Given, this does not make any sense for the average Person at all and yes, it's a lot of money and arguing if objectively *G for a year is worth the 3k $: It is probably not. But then again, if I have the money, the time and have fun in doing it then why the heck not?