According to Oricon, the first album CD of K-ON! titled "Houkago Teatime" was sold 67,000 copies and ranked the top in the weekly album CD sales ranking. It's for the first time in Oricon's history that an anime character's CD wins the top in the weekly music CD ranking. The total sales of the previously released six single CDs have reached 600,000 copies.

TBS released special guitar models for beginners reproducing Yui and Mio's guitars.

Yui's guitar on TBS ishop
Mio's bass on TBS ishop

For girls and teenagers, the guitars are made of light material (NATO). Both of them are priced 29,800 yen ($320).

The OP song of The Melancholy of Haruhi Suzumiya 2 "Super Driver" was sold 21,000 copies and ranked the third in the weekly single CD ranking.

Ref. The first week sales of Haruhi 1 OP and ED
Bouken Desho Desho 10th 13,996
Hare Hare Yukai 5th 34,881

Sources:
Oricon
Scan of Asahi Newspaper
Mainichi
Natsu Style

Related topics:
VA Mizuki Nana Wins The Top in the Weekly CD Ranking
Record Large Sales of K-ON! OP and ED CDs