I read, a while back, that they would possibly be unbounded. I had over 2k saved just for that reason. Sent them all to my Tailor and made dozen or so Royal Satchels.
"huge" as in like a couple of thousand gold maybe. they go for 15-20gold / spirit. so if you got 5 stacks of 20 thats a whopping 2000g.
Despite the increase stack size of Crafting Reagents and the advent of the Reagents Bank, currently Spirits of Harmony are giving the best return on Royal Satchels. I'm selling as many RS as possible foreseeing their steady drop in value as bag space becomes less of an issue in WoD. Certainly glad I stockpiled my SoH, was a pleasant surprise when they announced they were going BoE a while back!