John,
There are other good reasons to buy expensive rag papers than their supposed longevity; tactile experience, fiber strength, myths circling in the customer's mind, etc. Not all the rag papers keep their white; Photo Rag Bright White, quite new in Aardenburg testing, shows a fast change already. There have been more examples. The cheaper RC paper you quote did well in testing, both paper white and colors. So did the Aurora Natural. We do not know what the other properties will do in time; the bond of the coating to the paper for matte art papers and Fiber/Baryta, the reported cracking of coatings, the PE barrier/coating/fiber bonds, the PE decay.
Based on what we know I do not think you can say that the cheaper papers you are using or intend to use are inferior in longevity, that still has to be proven in practice or with other paper tests.
A rag paper like the Aurora can be produced and marketed at that price. There is just a smaller margin that should be enough for Red River the way they buy and distribute. The rag fibers will not be the longest in the market, the Fourdrinier will run fast, the 250gsm is only the 230 gsm I measured, the coatings will not be the 3 layers of HM Photo Rag and Dmax + Chroma will be accordingly. I have only one sheet printed on a B9180 and it is not bad. What might be an issue is the consistency between batches and what Red River will do with returns. Unlikely that the margin covers that. Watch the DPreview printing list and the Yahoo B&W list for any Red River issues, Red River has a wide group of fans there.
The HP Matte Litho-Realistic, if produced in a similar way offset papers are produced and with the same quality checks, may prove to be consistent. I expect the paper white to shift but the 20 Megalux results are encouraging. Several prints hanging here, bare as well but spray coated then and I am not complaining. Aardenburg measures a 16.6 L for Z3200 Dmax. More density than measured on several HM matte rag papers. Visually it is less black though in my experience.
met vriendelijke groeten, Ernst
330+ paper white spectral plots:
http://www.pigment-print.com/spectralplots/spectrumviz_1.htm