"we don't know the rebates we could earn to offer discounts to clients".
Er, chaps, I think that's the point.
If all you are competing on is the discount you appear to offer, then you should not be playing the game. If you have more to offer than bigger discounts than your competitors, you are better placed to survive beyond the next two quarters.
Or so say the know-it-alls in HQ, who've never actually been near a corporate purchasing department. But I understand where they're coming from, even if they are in cloud cuckoo land.