Harmonix has said Nirvana album "Nevermind" was never confirmed as DLC for Rock Band, but only ever used as an example of what could be offered.
"Nevermind" was mentioned back in July 2007 as one of the albums to be added to Rock Band after launch.
Yet, despite an admirable amount of DLC added using that timeframe, it took until April this year for the first album - "Screaming for Vengeance" by Judas Priest - to appear as DLC.
The most recent album released was "Doolittle" by The Pixies, which cost a meaty 1520 Microsoft Points (GBP 13 / EUR 18). Prices tend to vary.
Rock Band is only available in Europe on Xbox 360 for the time being. Distributor EA is keeping PS3, PS2 and Wii dates guarded.
The US will see Rock Band 2 released as a timed exclusive for Xbox 360 later this month, with instrument bundles to follow in October.
European dates are missing, a bit like Timmy Mallet's career.