I wouldn't worry so much about the 'high mileage', assuming you're thinking 20~30k is 'high'.
If the maintenance has been kept up, stored indoors, not thrashed, etc. that's not really any worse than a car with comparable mileage.
I recently bought an '06 GSXR-750 with 28k miles at a
stupid low price because the owner had himself convinced it was 'worn out'. It only needed chain/sprockets & a little TLC. Hell, the valves were still dead-on, and it feels just as tight (a bit smoother, if anything) as Kathy's when it was nearly new.