I'm with everyone else. If you like the paint job, look around and you can probably get an '01 for more like $2,500 and paint it yourself for about $500, putting you with another $1,000 in your pocket for other extras. IMHO half the fun is buying stock and customizing it yourself.
If that's a artist paint job and not a decal job it probably cost a few thousand dollars. I personally don't like it but if you do you'll be hard pressed to find another looks a lot like a one of a kind.
Don't be thrown off by the $4000 firm if you really want it make an offer he can only say yes, no, or make a counter offer.
For me, that "custom paint job" knocks what I'd offer for the bike DOWN about $1500, since that's what it would cost to get the bike repainted! I hate custom paint jobs, and that one is particularly ugly! I wonder sometimes if people who paint their bikes like that are mentally stable. I'm serious.
Besides the paint, it's a 13 year old, 800cc bike, and you can buy nicer ones (that you DON'T have to repaint) for a lot less than that one!
Uucccggh! I wouldn't take that bike for half that price. I say go for a bike like the ones diehard posted. If you're willing to pay that kind of money, get bike with a nice fairng or a lot of OEM aftermarket parts or something. Don't pay mpre for someone elses' "custom paint job".