I sold my immaculate zx636 on an '06 plate with 18,000 miles on the clock for £3,300.
There are cheaper, lower milage bikes out there than the one you are looking at for that money. But like it has been said, that sort of milage is average.
I got a 2000 R1 at the moment which when I bought it in March had 37,000 miles on it. Its now up to 43,000 and the motor still sounds sweet and doesnt miss a beat. As long as they have been looked after, regular oil changes, they will go forever and a day. Unless its a Triumph. They just blow up for no reason anyway.
Unfortunately now is not the time to be buying. Sell in the summer, buy in the winter.