The film we're buying now could have been made a year or two ago and kept frozen and chopped and sent to B&H/Freestyle/Adorama/wherever last week. It's probably not a just-in-time inventory business. We just don't know.
They've probably also hedged their silver to avoid increases which means they avoid some of the decreases too. Southwest for example hedges on jet fuel, and when companies do that they are less likely to be put out of business from supply cost volatility.
They also have no need to lower their prices if costs go down. It's not a regulated utility. It's a business that will lower their prices if they have to or if it makes sense to.