Hi,
TOO MUCH!
I had this model when I traded up to my ZZR600 in December 2002.
10,000km PERFECT condition, run as per the manual, full service history, Ventura rack...couldn't get (as a trade in) any more than
$4000 (and this was nearly two years ago).
Most offered $3000-$3500, best offer was Peter Stevens (where it came from) who felt sorry for me and gave me $4k. Having said that, in December 2002 they still had brand-new 2001 GPX250s for $6k + ORC, so in that light, $4k is a pretty good deal. The 2004s aren't much more in Peter Stevens now, and I've never seen them anywhere near RRP in any year.
Good little bikes, apart from the weird size wheels...limits tyre choices.
HTH, feel free to PM if you need any more info.
PS> Ask your mate to get a quote on how much they'll give him for a trade in and offer him a bit more.