>most of the time DRAM has not been available at these
should make it not the floor. If the floor doesen't have to be available, then what's the exact point it becomes relevant? Otherwise the price is simply misleading
A price has to be massively available at a point in time to matter. It doesn't have to be available forever to matter. It feels like you're conflating the two.
The price is on a downward trend, but there are hitches and setbacks. One fair way to measure it is to use some kind of average. Another also-fair way to measure it is to go by the lowest "real" price, where "real" means you can buy something like a million sticks on the open market.
When we're talking about whether we should be impressed by a price, using the lowest historical price for comparison makes sense.
(And just to be absolutely clear, you would need to adjust the metric for a product that goes up in price over time. But for something on a downward trend, this metric works fine.)