Does seem very cheap. Paid £1800 for my 2003 FZS600 with 13K on clock. Was spotless though, year MOT left, with DB screen, hugger, belly pan, meta alarm and some luggage thrown in.
I guess, do check usual stuff:
Does it need new tyres? ~£100 each.
Rusted downpipes (look underneath where it goes 4=>1). £250 buys you Motad stainless pipes and can.
Forks: check for pitting, and leaky seals.
Check oil: check not milky - sign of coolant leak and possibly big trouble.
Back brakes can sometime seize and need thorough cleaning.
Check chain for stuck/rusted links, hooked teeth on sprocket etc. Budget £120 odd for new parts.
Has it been dropped: Look for scuff on sides of fairing, cracks under indicators, scuffed bar ends, clutch covers etc. Sit on it and double check fairing, clocks and lights are pointing dead straight. After a drop the fairing bracket often bends, leaving the front end skew-if and is a right pain to bend back perfectly straight again. Check mirrors are good, fold fine and firm when out. Often break in a drop and there's no good substitute for a £90 genuine new one.
Check for general wear'n'tear, seat, peg rubber, bar grips, knee scuffs on tank etc, does it look indicative of the mileage? Get the past MOT number and look up history on gov website, see if mileage on past tests syncs up. Check what advisories/fails it previous had. These can sometimes give you an idea what happened to bike and how well it's been maintained.