Silver Sophie cost me $2000, in May, and that was a not-unreasonable price for hereabouts. What I got was a 'runner' with everything original, except for the front brake master cylinder/reservoir. As I have noted before she was good to go, and carried me 200 miles home over the mountains.
Of course, since then she has cost me $$ for chain/sprockets/rear tyre/Scottoiler (yeah, my choice, I know!)/air cut-off valves in the carbs....plus the replacement (proper) front brake stuff and carb rebuild kit waiting to be dealt with.
Japanese bikes that run seem to bottom out at about $1500 here, regardless of motor size or model. To find anything cheaper, as I mentioned before, you are looking at a non-runner which will require lots of $$. Or you have to be really lucky!