at 600k gold its much less a gold sink as its a gold reset.
In order for this to be called a gold sink its going to require that a.)people want to do it, and b.)People can afford it. I think it would be much more reasonable that people would spend say 75k-100k gold in order to reforge their weapon.
The sink part comes in that more people will be able to do it, Nothing is gained by doing it, your just replacing the weapon.
Something else to think about is putting a Cap on the number of times something can be reforged before it has a chance to be destroyed. Maybe you can reforge it 3 times, then everytime after that there is a 25% chance the weapon is destroyed.