Mileage in itself is not an issue, to me.
My '57 plate bike I've had from new has 28,000 miles on the clock. Black Bear Harley offered me a rubbish price on it, as they were basing it on "book price" of 9,000 miles. :roll:
Someone I know, had a 10 year old bike with 50,000 miles on the clock and all the dealers were messing him about for trade in, £500 tops, he sold it for £1k privately.
Condition, service history would be important to me. I'd probably want a mate who knows about mechanical stuff to check a second hand bike over with me before I bought it too.
But mileage, on it's own, not an issue for me.
p.s I nearly bid on Paddy Tyson (one of the MAG leading lights) used pan european with 125,000 miles on ebay last year, but the wife was being awkward