You are correct. Finding .308 is nearly impossible — coast to coast. And, those who have .308 are selling insane prices, as in, more than double the cost of standard prices.
So, I understand what the blogger is saying, and I suspect you are right that while making his point he was playing a little loose with the stats.
Whatever the case, I do hope supply comes back into congruity with demand soon. Nobody wants to go to the range and shoot ammo that they cannot resupply.
That is the real problem; I have enough ammo for any real need, but I'm not going to burn it up at the range anymore.