Oh boy, lot of new insights in the last few posts.
I first became aware of the Atlex.com price for 44 inch 40 ft length Entrada Rag Natural 300gsm (yes, the premium thickest paper of all the Entrada versions and double-side coated to boot) several months ago. At first I thought it was an error because ITSupplies doesn't list it at the same price, and ITSupplies and Altlex.com are strongly affiliated. Perhaps Atlex who is posting in this thread can clarify the exact relationship between ITSupplies and Atlex.com. But that price point has held for quite some time, so I'm inclined to take Atlex at his word. It's the real deal price at least for now!
Second, Hahnemulhe actually offers very few OBA-free papers in its diverse lineup of media. HN Museum Etching, William Turner, Photo Rag Pearl, and Photo Rag Baryta are, as far as I know, the only ones out of over 20 different media supplied by Hahnemuhle that are completely OBA-free. That said, several (but not all) Hahnemuhle papers use OBAs very sparingly, i.e. only in the paper core not in the coatings, and at relatively low levels. Location in the media composite layers and concentration levels of the OBAs are both critically important factors in how well papers containing OBAs perform in Aardenburg light fade testing. So, papers like HN photo Rag which have low OBA content and only in the paper core generally perform quite well in Aardenburg testing, albeit not always quite as well as full OBA free media like HN Museum Etching, but well enough that the enduser can be confident in the long term visual appearance of the media whitepoint color. It is the slight tweaking of the media whitepoint color with OBAs in the paper core that gives Hn Photo Rag a slight edge over HN Museum Etching, Moab Entrada Natural, and RR Aurora Natural in terms of measured b* "neutral" whitepoint value, but all of these papers range from b*= 0.0 to about 2.5. Hence, while some are a little more neutral than others none appear to be "cool white" or bright white" in color. If Bright and cool white color balance is your thing, but you also want long term image permanence, then get over your OBA impregnated cool white media bias and learn to dial in a little more "coolness" into your digital image file before you print it
...Just sayin, it's a file prep issue not an inherent drawback when using warmer whitepoint media as long as they are not too warm.
Third, HN Photo Rag UltraSmooth just underwent a reformulated coating according to a recent post I read by Keith Cooper either here on LULA, or perhaps I saw it on DpReview. He was privy to a client bulletin from Hahnemuhle stating as such. Anyway, that means Photo Rag Ultrasmooth should ideally be retested with various ink sets for light fastness performance, but my guess it that the new version will still have low OBA content only residing in the paper core not in the coating. It will likely perform reasonably well, and endusers of HN low OBA content media should be reasonably confident in the overall longevity of the media itself irrespective of the longevity of the inks they use. That said, note that Hahnemuhle also makes some premium priced media which crank up the OBA content, locate it in the ink receptor coating as well, and thus all bets are off with those HN products in terms of long term media whitepoint stability.
There may also be one more wildcard in the OBA content story, namely the presence of titanium dioxide (TiO2). Essentially all resin coated (RC) photo media contain a pigmented TiO2 whitening layer, bit some non RC media incorporate TiO2 as well, and in conjunction with OBAs, this chemistry produces some nasty additional yellowing that goes beyond the mere OBA burnout result. It grows additional media discoloration when the artwork is retired to dark storage conditions or exhibited on display at lower light levels that aren't able to bleach this stain formation away like many accelerated light fade testing units do (which is why this phenomenon has gone largely unnoticed and under reported in the ratings for so long in the industry).
Best advice: look for media that have low OBA content in the paper core only or none at all if you care about preserving the whitepoint and highlight, even midtone colors, for as long as your OEM pigmented inks are capable of providing on their own merits.
cheers,
Mark
http://www.aardenburg-imaging.com 
