I suggest you find out where the oil is going: it's either leaking out somewhere, or going out the exhaust pipe. That kind of usage seems a bit high to me. How many miles on the engine? Any work done on it recently?
Pull the plugs and see if any of them are black and oily looking. Possible causes are worn valve guides or seals, possibly tired oil rings on the pistons. Check the exhaust pipes: oil will make the inside of the pipe very black.
It's also possible it's leaking somewhere. Any drips on the garage floor after it's been sitting overnight? Check all around the engine where pieces come together. Is your chain oily, especially if you haven't lubed it in a while? Oil filter tight enough? Loose bolts anywhere?
Hope this helps.
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.