The reason why some manufacturers won't quote you, is generally it's a waste of their time. Not that you won't go forward, but I've done a lot of wholesale nutraceuticals and the great majority of people who call in asking for custom runs don't end up going forward - even when we have the best price. It seems that in many cases it's just a spur of the moment idea of theirs that they don't have real intentions on going forward on.
Still, for a new formula/product, you usually need a minimum run of 1000 units. If you have that, manufacturers should be able to give you an estimate pretty quickly.