Glyph books made all kinds of sense in Wrath, when they were obtainable anywhere by anyone. Now that they're only dropping for people as they level, the supply has plummeted. New scribes are having their short hairs held over the fire by the people who will end up paying too much for their glyphs, so I suppose it's a probably fair, but Blizzard is changing it.
Coming soon, new scribes will be able to finish learning their glyph books by research alone, and books will only be an added bonus. This will reduce the price for them, as cheap scribes who are willing to wait will no longer be snatching up any inexpensive books they find.
If you have any of these books that you're trying to flip for a profit, use them or sell them quickly, before the mat is pulled from under you. Take heart; I still have at least six Tomes of Polymorph: Turtle in a storage guild bank somewhere that I took a bath on. That's all part of the fun of speculation, and it makes wins feel better.
Maximize your profits with more advice from Gold Capped as well as the author's Call to Auction podcast. Do you have questions about selling, reselling and building your financial empire on the auction house? Basil is taking your questions at firstname.lastname@example.org.