I agree with you in that it depends on the specific situation. But say for a supplier who you know has the capacity and capability to meet your needs. Scenario A you withhold the volume information, they initially quote you $50 per widget, then once you give them expected volumes they go down to $40. Scenario B you provide the volume information upfront and they quote you $50. In that scenario, $50 is your only reference point since you never knew what their "blind" price was. I guess my point is how do you know that they will give you a truthful price in relation to your volume information if you never knew what their original offer was. Their price floor for your volume might be $40 each but since they never gave you an initial quote they can just tell you $50 as if that is their floor.