A couple things: Since the original poster enquired about discount pricing, I doubt that either Light Impressions nor Superior Archival count, as both cost about as high as I've seen.
But if you consider long-term survival of the product, and if the claims made for Superior's Alpharag are true, then the Alpharag mats start looking much more economical.
But as a chemist, I have trouble with Mr. Smith's experiment as described. The amount of test description is woefully inadequate, even for the lowest standard of a scientific test. For example, the concentrations (or partial pressures) of the components of the "pollution" gas need to be described (including the all-important humidity), whether either of the boards contained buffers (if I follow the product descriptions properly, neither was buffered, but it isn't explicit), the extent of the natural buffering provided by zeolites (as opposed to molecular trapping), the pH of the boards after the test, how long the test was done, and at what temperature.
But the absence of one test is, I'm afraid, quite telling: Alpharag vs. buffered paper. Superior makes the claim that zeolite trapping is more effective than buffering, but this claim is never tested. It's Superior's strongest claim, but oddly remains unproven.
Is a whitepaper perchance available describing the tests in full?