If you're looking at Craigslist, I might suggest opening up your search radius to your state and surrounding states (assuming you're in the US of A). Sometimes you'll get a better deal if you're away from a major metro area, even if it might take some dollars getting it into a truck/van and back to your place.
Here in the central Ohio area, you could pay anywhere from 800-2500 or more for CB750s in various condition.
I second the suggestion of asking others, let them know you're interested in an inline 4 Honda bike, and see if you can get others to hunt around.
Luke M
Used to have a 1979 CB750L, sold it as a parts bike, now riding a slightly modified 1984 VT700C. Network/Field Engineer. Central OH, USA, Earth, Sol System, Milky Way Galaxy, Universe.