Target has them permanently discounted to $7.49 in the US since June, and some of the stores still have pretty good variety--the one nearest to my work had Magic, Light, Undead, Life, Earth, Water and Air when I stopped by last night, and the one nearest my house had multiple Tech crystals this past weekend. I haven't seen Dark crystals at a Target since May though.
I haven't seen any sales on them at any other stores for a few months. Even Toys R Us, who usually has tons of Skylanders sales, keeps excluding Imaginators toys when they've done sales this year.
(If you meant something else, then, uh, please clarify.)