That's a fair question Rod. My thinking is that since the arrival of the (in my opinion) far superior Vario and similar pages, the cost of a good sorting page has come down, even considering inflation.
For example, an eBay
seller from whom I have bought offers Vario pages at US$18.45 for 25 pages, or around 74c each…with free shipping!
So, what is a fair price to pay for Manila stock pages? It is almost like asking, "How much would I pay for a 1940's washing machine with a wringer attachment?"
Honestly, for the Manila pages I would have to say that anything above 75c/sheet would be too much to pay.