An appeal was launched last year when news of Karn's illness was announced.
Porcupine Tree - a band featuring former Japan keyboardist Richard Barbieri - were among those who donated profits from auctions and album sales.
Punk alternative
Born Adonis Michaelides in Cyprus in 1958, Karn emigrated to London when he was three years old.
His official biography tells how he bought his first bass guitar for £5 after a bassoon he played in an orchestra was stolen.
He formed Japan in 1974 with David Sylvian and the latter's younger brother Steve Jansen, performing for the first time when Karn was 15.
The band's albums include Quiet Life and Adolescent Sex
Having been joined by Richard Barbieri, another school friend, Japan landed their first record contract in 1977.
With their dyed hair and make-up, Japan offered a "glam" alternative to punk and later became associated with the New Romantic movement.
After Japan split in 1982, Karn continued to work on solo projects and recorded with Kate Bush, Gary Numan, Midge Ure and Joan Armatrading.
Karn briefly reunited with other members of Japan in 1991 for the one-off project Rain Tree Crow.
Tributes have been left on Karn's website, with one fan saluting his dexterity with the bass.
"No one will ever touch him on the fretless," wrote 'ngriff' on Wednesday. "He shaped the way that instrument is played like no other."
BBC presenter Jeremy Vine has also remembered the musician's "sensual and stylish" playing.
