Auctioned off by Christie's of New York.
Sears model bass guitar, serial number 20180. According to Cobain's Aunt Mari Earl, Cobain recorded his first demo at her home in Seattle using this bass. The demo was called "Organized Confusion" a name he wished to call his band. In 1985 Cobain recorded a second demo also using this bass called "Fecal Matter". On June 23, 2009 the bass was sold to a private collector at a Chrysties auction in New York for $43,750. Article on sale here.
From NPR article;
"Going for an estimated $60,000-$80,000, this Sears model bass guitar was used by Kurt Cobain to record his early demos at his aunt's home in Aberdeen, Wash. The item comes with an image of a teenage Cobain playing the bass, and a letter from his aunt regarding the provenance of the guitar."