One way to go is look up a bike that interests you on fuelly.com. Almost at random at the moment I see a naked 2006 Suzuki SV650 with less than 6K miles that just popped up on on Portland craigslist
(but a Vancouver bike) for $3500.
I was looking at SVs and VStroms around then and I noticed the nakeds were harder to find than the sport fairing version at the time. Poster claims 60mpg "if you ride easy", which suggests to me you'd want to check all his claims pretty carefully, as that doesn't seem to agree with anyone else's real world experience
. Also the price seems a little low for the mileage, though the SV was just a bit dated for its class even then.
On the other hand nearly 50 overall seems fairly common and is good for a proven and bulletproof bike like the Suzuki. I ended up getting a VStrom back then (07); same engine but of course a somewhat different build and I don't quite remember the mileage. 47 sounds about right. (Great bike and I kind of miss it even it it wasn't a perfect fit for my demands.)